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CHEMISTRY 
IN  THE   HOME 


BY 

HENRY  T.  WEED,   B.S, 

HEAD     OF     SCIKNOR     DEPARTMENT 

MANUAL  TRAINING    HIGH   SCHOOL 

BROOKLYN,    N.  Y. 


AMERICAN   BOOK  COMPANY 

NEW  YORK  CINCINNATI  CHICAGO 


Gift 


COPYRIGHT,  1915 
BY    HENRY    T .   WEED 


WEED.       CHEMISTRY    IN    THE    HOMK 
W.   P.    I 


PREFACE 

THIS  book  is  the  product  of  an  effort  to  meet  the  needs 
of  students  who  elect  chemistry  early  in  their  high  school 
coarse.  It  aims  to  train  students  in  scientific  thinking 
and  to  give  them  a  fund  of  information  concerning  the 
chemistry  of  everyday  things,  related  to  industries  and 
the  home. 

Much  of  the  theory  common  to  high  school  chemistries 
has  been  omitted,  because  it  has  been  found  to  be  unnec- 
essary, in  fulfilling  the  purpose  of  this  text.  Constant 
effort  has  been  made  to  keep  the  language  and  style  sim- 
ple and  to  select  subject  matter  suitable  for  boys  and 
girls  in  the  lower  classes  of  the  high  school.  The  book 
represents  the  result  of  many  trials  and  much  elimination 
from  an  overcrowded  field  of  subject  matter. 

It  would  have  been  impossible  to  prepare  the  book 
without  the  efficient  aid  of  my  colleagues  of  the  Manual 
Training  High  School  of  Brooklyn,  New  York.  I  wish 
especially  to  thank  Dr.  Charles  D.  Larkins,  the  principal 
of  the  school,  to  whose  suggestions  the  book  is  primarily 
due,  Mr.  Charles  Germann,  who  has  read  the  proof  and 
made  numerous  suggestions,  Dr.  William  Lamb,  Mr. 
Mattuck,  Mr.  Holly,  and  Mr.  Foster.  Mr.  Frank  Rex- 
ford,  of  Erasmus  Hall  High  School,  Brooklyn,  has  allowed 
the  use  of  his  food  tables  for  use  in  the  food  chapter, 
and  assisted  in-  the  preparation  of  the  chapter.  Miss 
J.  Jenness,  of  the  Girls  High  School  of  Brooklyn,  has 
used  the  notes  in  her  classes  and  has  made  many  helpful 
suggestions. 

445110 


CONTENTS 


CHAPTER 

I.  PHYSICAL  AND  CHEMICAL  CHANGES   . 

II.     WATER 

III.  SOLUTION 

IV.  OXYGEN  AND  HYDROGEN  PEROXIDE  . 

V.     HYDROGEN 

VI.     ATOMIC  THEORY 

VII.     COMBUSTION 

VIII.     HKAT 

IX.     THE  ATMOSPHERE 

X.  FORMULAS,  EQUATIONS,  AND  VALENCE 

XI.  CHLORINE       ....... 

XII.  ACIDS,  BASES,  AND  SALTS    .... 

XIII.  SODIUM  AND  ITS  COMPOUNDS 

XIV.  AMMONIA  AND  AMMONIUM  COMPOUNDS 
XV.     METALS 

XVI.  PHOTOGRAPHY 

XVII.  CARBON  AND  ITS  COMPOUNDS 

XVIII.  THE  OXIDES  OF  CARBON     .... 

XIX.  BAKING  POWDERS          .        .        . 

XX.  HYDROCARBONS  AND  DERIVED  COMPOUNDS 

XXI.  OILS,  FATS,  AND  SOAPS       .... 

XXII.  CARBOHYDRATES    ...... 

XXIII.  FOODS 

XXIV.  FOOD  PRESERVATION     .        .        .        . 
XXV.  SILICON,  SILICA,  AND  SILICATES 

XXVI.     TEXTILES 

6 


PAGE 
9 

14 

27 

38 

44 

48 

58 

76 

96 

109 

123 

130 

137 

145 

149 

166 

175 

188 

195 

202 

211 

225 

250 

283 

304 

316 


CONTENTS 


CHAPTER 

XXVII.     LAUNDRY  CHEMISTRY         . 
XXVIII.     THE  CHEMISTRY  OF  COOKING   .         •  N      • 

PAGE 

.     325 
.     332 
.     336 

XXX.     DYES  AND  DYEING     
XXXI.     SOME  COMMON  CHEMICALS 

APPENDIX: 
METRIC  MEASUREMENTS        
PHYSICAL  CONSTANTS  OF  COMMON  ELEMENTS  . 

INDEX  . 

.     346 
.     354 

.     377 

.     378 

379 

CHEMISTRY   IN  THE   HOME 

CHAPTER  I 
PHYSICAL  AND   CHEMICAL   CHANGES 

Importance  of  science.  Every  thinking  person  realizes 
that,  in  order  to  get  the  most  out  of  life,  it  is  necessary  to 
understand  the  laws  that  govern  the  world  in  which  we  live. 
The  consequences  of  not  understanding,  or  of  disobeying, 
these  natural  laws  cannot  be  evaded.  The  State  may  make 
a  law  ordering  us  to  pay  a  tax  upon  bonds  which  we  may 
own.  An  unscrupulous  person  might  evade  the  payment  of 
this  tax  and  thus  prevent  the  carrying  out  of  the  law. 
It  is  not  so  with  the  laws  of  nature.  Nature  never  employs 
courts  and  officers  to  carry  out  her  decrees.  If  we  violate 
her  laws,  the  penalty  is  certain  to  follow,  hence  the  import- 
ance of  understanding  and  obeying  these  laws.  Moreover, 
the  laws  of  nature,  unlike  man-made  laws,  never  change,  so 
that  what  we  learn  of  them  in  our  study  of  chemistry,  will 
be  of  use  to  us  throughout  life. 

We  must  not  think  of  physics  and  chemistry  as  studies 
useful  only  to  those  who  expect  to  engage  in  technical  pur- 
suits, but  as  everyday  studies  that  will  help  us  to  live  more 
satisfactory  lives,  because  they  help  us  to  understand  the 
reasons  for  the  numerous  things  that  we  must  or  must  not 
do  if  we  expect  to  secure  the  greatest  amount  of  health  and 
enjoyment  from  life. 

9 


10 


CHEMISTRY  IN  THE  HOME 


Mattel;  is;  .continually,  changing.  As  we  consider  our 
everyday  ;life,' we  see 'that  one  of  the  most  .striking  things 
about  it  is,  that  there  is  everywhere  continual  change.  Our 
clothes  wear  out,  iron  rusts,  trees  decay  and  die,  even  the 
rocks  that  seem  so  everlasting  crumble  and  change  to  soil. 
Our  world,  then,  is  not  an  unalterable  mass,  but  is  in  a 
constant  state  of  change,  and  what  we  must  do  is  to  learn 

to  understand  and  direct 
these  changes,  so  that 
they  may  be  for  our 
benefit,  and  not  for  our 
injury.  This,  man  is 
slowly  learning  to  do. 
Until  we  had  learned 
the  cause  of  decay,  we 
could  not  know  how  to 
prevent  it,  but  now  that 
we  understand  the  rea- 
sons why  foods  spoil,  we 
can  prevent  such 
changes.  Scientists  are 
constantly  studying 
these  changes  which 
take  place,  and  finding  out  how  to  use  them  to  our  ad- 
vantage. When  we  examine  these  various  changes  care- 
fully, we  find  that  they  are  divided  into  two  great  classes, 
physical  and  chemical. 

Physical  changes.  When  you  cut  out  and  make  a  suit, 
you  have  changed  the  shape  of  the  cloth.  You  have  taken 
cloth,  thread,  buttons,  and  lining.  You  have  changed  the 
relative  arrangement  of  all  these  materials,  but  every  particle 
of  the  cloth,  thread,  buttons,  etc.,  is  still  in  existence  as 


FIG.  1.  —  Crumbling  rock  makes  soil. 


PHYSICAL  AND  CHEMICAL  CHANGES  11 

cloth,  thread,  buttons,  etc.  When  the  suit  is  worn,  you 
brush  against  the  furniture,  and  tiny  pieces  of  the  cloth  are 
worn  off,  but  they  are  essentially  the  same  cloth  particles. 
Such  changes  as  these  are  called  physical  changes. 

Mixing  a  batter,  boiling  water,  and  the  falling  of  rain  are 
other  examples  of  physical  changes;  in  general  the  science 
of  physics  is  the  study  of  such  changes.  We  see  ourselves 
reflected  in  mirrors,  our  trolley  cars  run,  we  telegraph  and 
telephone,  by  taking  advantage  of  the  laws  governing  such 
physical  changes.  Physical  changes  are  those  in  which  the 
composition  of  the  small  particles  of  the  original  substance 
remains  unchanged. 

Chemical  changes.  If  we  tear  up  a  newspaper,  we  illus- 
trate a  physical  change,  since  every  particle  of  the  original 
paper  is  still  in  existence.  If,  however,  we  set  fire  to  the 
paper,  a  different  kind  of  change  takes  place.  The  paper 
particles  disappear,  and  new  substances  (a  white  ash  and 
an  invisible  gas),  having  new  properties,  take  their  place. 
Such  a  change  as  this  is  a  chemical  change,  and  the  study 
of  such  chemical  changes  and  the  laws  which  govern  them, 
constitutes  the  science  of  chemistry. 

Importance  of  chemical  and  physical  changes.  It  is 
difficult  to  overestimate  the  importance  of  the  study  of 
these  chemical  changes.  The  beautiful  colors  of  silks  and 
ribbons,  that  so  delight  the  eye,  are  produced  by  dyes  ex- 
tracted by  a  chemist  from  black,  vile-smelling  coal  tar  by 
chemical  processes.  The  rails  on  which  our  trolley  cars 
run  are  possible  only  because  a  chemist  found  how  to  extract 
iron  cheaply  from  its  ores  by  chemical  changes.  The  proper 
selection  of  foods  for  the  home  may  be  made  when  we  have 
learned  of  the  chemical  changes  which  each  type  of  food 
undergoes  in  digestion,  and  the  body  requirements. 


12 


CHEMISTRY  IN  THE  HOME 


Often  actions  which  we  wish  to  study  include  both  physical 
and  chemical  changes.  In  the  making  of  bread,  the  mixing 
of  the  flour  and  water  is  a  physical  change,  but  the  action 
of  the  yeast  in  making  the  bread  light  is  a  chemical  change, 
so  that  the  baked  loaf  is  a  result  of  both  physical  and 
chemical  changes.  Every  day,  in  a  hundred  different  ways 
we  are  making  use  of  both  physical  and  chemical  changes. 
Let  us  at  the  very  beginning  try*  to  understand  and  ap- 
preciate the  importance  of  the  study  of  these 
physical  and  chemical  changes  in  their  rela- 
tions to  our  everyday  life. 

Matter  is  indestructible.  In  many  of  these 
physical  and  chemical  changes,  there  seems  to 
be  a  destruction  of  matter.  When  a  candle 
burns,  it  disappears,  and  our  natural  conclusion 
is  that  the  matter  composing  it  has  been  de- 
stroyed. It  is,  however,  not  safe  for  us  to 

FIG.    2.  —  Mat-    .  -,  *  TTT     i  ,* 

ter  is  not  de-  JumP  at  such  a  conclusion.       We  know  that 
stroyed  m  our  impressions  are  not  always  to  be  relied 

burning. 

upon.  You  know  how  difficult  it  is  to  deter- 
mine by  your  feelings,  whether  a  room  is  at  the  proper  tem- 
perature or  not,  and  how  necessary  it  is  to  correct  your  im- 
pression by  consulting  a  thermometer.  You  know  how  im- 
possible it  is  to  estimate  the  size  of  a  room,  or  to  guess  a  person's 
weight  accurately;  but  with  a  yardstick  you  can  measure 
the  room  and  with  a  scales  you  can  find  a  person's  weight. 

You  must  always  try  to  find  a  way  to  test  the  truth  of 
your  impressions,  and,  in  the  case  of  the  candle,  the  test  is 
easy.  If  you  place  a  candle  in  a  large  bottle  filled  writh  air, 
seal  the  bottle,  weigh  it,  and  then  set  fire  to  the  candle  with- 
out opening  the  bottle  (which  can  be  done  by  the  aid  of  a  burn- 
ing glass),  you  are  sure  that  no  matter  can  either  get  into  or 


PHYSICAL  AND  CHEMICAL  CHANGES  13 

escape  from  the  bottle  (Fig.  2).  The  candle  will  burn  for 
a  time,  and  then  go  out.  If  you  allow  the  bottle  to  cool, 
and  then  weigh  it  again,  you  will  find  that  its  weight  has  not 
changed.  That  is,  the  materials  making  up  the  candle  have 
formed  new  combinations  with  the  air,  and,  these  new  sub- 
stances, being  colorless  gases,  usually  escape  bur  notice.  No 
matter  has  been  destroyed,  and  no  matter  has  been  created, 
but  new  substances  have  been  formed,  the  total  weight  of 
which  is  the  same  as  that  of  the  original  candle  and  air. 

Similar  experiments  verify  the  fact  that  the  total  weight 
of  the  new  products  is  always  equal  to  the  total  weight  of 
the  original  substances.  We  can  neither  create  nor  destroy 
matter.  All  we  can  do  is  to  change  its  combinations.  This 
is  the  Law  of  the  Conservation  (or  Indestructibility)  of 
Matter :  Matter  can  neither  be  created  nor  destroyed. 

SUMMARY 

Matter  is  anything  that  occupies  space. 

A  physical  change  is  a  change  in  which  no  particles  of  matter  dif- 
ferent in  composition  from  the  original  substance  are  formed. 

A  chemical  change  is  one  in  which  the  particles  of  matter  in  the 
original  substance  are  so  altered  that  the  identity  of  the  indi- 
vidual particles  is  destroyed. 

Law  of  Conservation  of  Matter :  Matter  can  neither  be  created  nor 
destroyed. 

Exercises 

1.  Name   three  common  chemical   changes.      Three   physical 
changes. 

2.  Are  the  following  changes  chemical  or  physical?     Rusting 
of   iron.     Striking   a   match.     Beating   an    egg.     Making   coffee. 
Sweeping.     Digesting  food. 

3.  A  ton  of  coal  when  burned  will  produce  only  about  230  pounds 
of  ash.     Is  this  not  a  case  of  the  destruction  of  matter  ?     Explain. 

4.  Iron  rust  weighs  more  than  the  iron  from  which  it  was  made. 
Has  not  matter  been  created  ?     Explain. 


CHAPTER  II 
WATER 

Occurrence  of  water.  Water,  a  tasteless  and  odorless 
liquid,  is  one  of  the  few  indispensable  substances  of  the 
earth.  It  is  found  even  m  places  where  no  visible  trace  of 
its  presence  exists.  The  paper  on  which  these  words  are 
printed  contains  about  8%,  the  solid  rocks  contain  a 
small  amount,  and  our  foods  are  largely  composed  of  it. 
The  table  below  shows  the  amount  of  water  present  in 
some  common  substances. 

Bananas      ....  75  %  Eggs 74  % 

Beef,  rib  roast      .     .  44  %  Our  bodies    ....  65  % 

Cabbage      ....  78  %  Potatoes 78  % 

Cheese 31  %  Wheat  flour       ...  12  % 

Properties  of  water.  When  we  cool  water  to  32°  F.,1  it 
changes  to  a  transparent  solid,  colorless  in  small,  and  light 
blue  in  large,  masses.  Ordinary  ice  is  not  perfectly  clear, 
because  the  water  from  which  it  is  made  contains  air  dis- 
solved in  it,  and,  on  freezing,  this  air  is  distributed  through 
the  ice  in  the  form  of  small  bubbles.  The  freezing  point  of 
water  is  the  same  as  the  melting  point  of  ice,  namely,  32°  F. 

1  Our  ordinary  house  thermometers  are  graduated  on  what  is 
known  as  the  Fahrenheit  scale.  Fahrenheit  is  usually  abbreviated 
to  F.  The  name  is  given  in  honor  of  Dr.  Fahrenheit,  a  German,  who 
devised  the  scale. 

14 


WATER 


15 


Expansion  of  water.  Most  of  us  are  familiar  with  the  fact 
that  solids  expand  when  heated.  The  next  time  you  cross 
an  iron  bridge,  see  if  you  can  find  the  expansion  joint  pro- 
vided to  allow  for  the  expansion  of  the  iron.  Such  expansion 
joints  are  used  in  many  places  to  prevent  the  straining  of  the 
metal  that  occurs  when  it  is  held  rigidly  and  heated.  There 
are  many  such  expansion  joints  in  the  steam  lines  of  your 
school  building.  Figure  3  shows  a  section  of  one  of  these 


FIG.  3.  —  An  expansion  joint. 

expansion  joints  used  in  long  pipe  lines  for  steam  and  hot 
water.  See  whether  you  can  find  one. 

The  blacksmith  takes  advantage  of  this  expansion  of  iron  in 
putting  the  tire  on  a  wagon  wheel.  He  makes  the  tire  too 
small  to  go  on  the  wheel  while  cold,  but,  on  heating  the  tire, 
it  expands  sufficiently  to  allow  it  to  be  forced  on.  When  the 
tire  cools  again,  it  shrinks  and  grips  the  wheel  so  tightly  that 
it  stays  on  without  bolts  or  screws  to  hold  it. 

Water  expands  in  the  same  way  when  heated,  but  there  is 
an  unusual  fact  about  its  expansion.  If  we  start  with  water 
at  32°  F.,  its  freezing  point,  it  contracts  on  heating,  up  to  the 
temperature  of  39°  F.,  at  which  point  it  first  begins  to  expand. 
At  39°  F.,  then,  water  has  its  least  volume,  and  therefore  its 
greatest,  or  maximum,  density.1  That  is,  a  cubic  inch  of 

1  By  density  we  mean  the  quantity  of  matter  contained  in  a  given 
volume  of  a  substance.  A  cubic  foot  of  water  weighs  62£  pounds.  A 
cubic  foot  of  iron  weighs  437^  pounds.  These  numbers  express  the 
density  of  water  and  iron  respectively.  Volume  for  volume,  the 


16  CHEMISTRY   IN   THE   HOME 

water  at  39°  F.  weighs  more  than  a  cubic  inch  of  water  at 
any  other  temperature. 

As  a  result,  when  the  surface  water  cools,  it  becomes  denser 
and  sinks  to  the  bottom.  This  continues  until  all  the  water 
has  reached  its  temperature  of  maximum  density,  39°  F. 
Then,  as  the  surface  water  becomes  slowly  cooler,  it  becomes 
less  dense,  and  therefore  floats  on  the  surface  of  the  warmer 
water  beneath.  The  ice  forms  on  the  surface  and  acts  as  a 
protective  blanket.  Because  the  ice  is  a  poor  conductor  of 
heat,  the  water  below  freezes  very  slowly.  It  is  for  this 
reason  that  a  long  cold  spell  is  necessary 
before  we  have  skating  on  a  pond  or  lake. 
The  water  at  the  bottom  of  the  ocean  has 
about  the  temperature  of  maximum 

§  density,  39°  F.,  the  year  round. 

As  water  freezes,  it  expands,  and  it  is 
this  expansion  that  cracks  water  pipes. 
You  have  noticed  the  forcing  up  of  the 

CaP    °f    the   milk    b°ttle   in   Winter>  due    t0 

the  expansion  of  the  milk  in  freezing 
(Fig.  4).  This  expansion  is  the  reason  why  ice  floats  on 
the  water.  Can  you  explain  why  thick  cut  glass  dishes 
break,  if  put  into  hot  waterr  while  thin  glass  tumblers  do  not  ? 

Steam.  If  we  melt  ice,  and  heat  the  resulting  water  to 
212°  F.,  and  continue  the  heating,  the  water  boils,  that  is, 
changes  to  an  invisible  gas  called  steam. 

The  mist  that  is  commonly  called  steam  is  not  steam  at  all. 
Notice  the  spout  of  the  tea-kettle  when  the  water  is  boiling 
vigorously.  For  the  space  of  a  half  inch  from  the  end  of  the 

iron  weighs  seven  times  as  much  as  the  water,  or  a  cubic  foot  of  iron 
contains  seven  times  as  much  matter  as  a  cubic  foot  of  water.  The 
density  of  iron,  compared  to  water,  is  seven. 


WATER 


17 


spout,  nothing  can  be  seen ;  beyond  that  point  we  have  the 
mist  formed  by  the  steam  cooling  and  condensing  into  very 
tiny  drops  of  water.  That  is,  we  have  transparent  steam 
issuing  from  the  spout,  and  beyond  this  a  cloud  of  condensed 
steam. 

Water  boils  at  212°  F.  only  when  the  pressure  of  the  air  is 
normal,  that  is,  when  the  barometer1  stands  at  30  inches. 
At  Denver,  the  ordinary  air  pressure  is  much  less  than 
at  New  York,  owing  to  its  elevation  above  sea  level.  Water 
boils  in  Denver  at  about  202°  F.  This  makes  it  necessary 
to  boil  foods  longer  in  Denver  than  in  New  York,  as  the  tem- 
perature of  the  boiling 
water  is  so  much  lower 
there.  On  the  tops  of 
some  high  mountains,  it 
is  almost  impossible  to 
hard  boil  an  egg,  the  tem- 
perature of  the  boiling 
water  is  so  low.  =^^^$^  \j/ <•// 

Increasing  the  pressure     //f \  :^^|H   / 

raises  the  boiling  point. 
In  a  steam  boiler,  if  the 
pressure  is  100  pounds  per 
square  inch,  the  boiling 
point  of  the  water  is  raised 
to  337°  F.  Advantage  is  taken  of  this  fact,  in  boiling  meat 
and  vegetables  at  high  altitudes.  The  food,  with  water, 
is  placed  in  a  steam-tight  vessel,  called  a  pressure  cooker 

1  A  barometer  is  an  instrument  that  tells  what  the  pressure  of  the 
air  is.  This  pressure  varies  from  day  to  day.  When  it  is  sufficient 
to  make  the  barometer  stand  at  30  inches,  we  say  that  the  air  pres- 
sure is  normal.  (See  page  97.) 


FIG.  5.  —  A  pressure  cooker. 


18  CHEMISTRY   IN  THE  HOME 

(Fig.  5),  and  heated.  The  steam,  unable  to  escape,  increases 
the  pressure,  this  raises  the  boiling  point,  and  so  it  is  possi- 
ble to  cook  the  food  satisfactorily. 

Evaporation  of  water.  As  found  in  nature,  water  usually 
contains  impurities.  The  purest  form  is  rain  water,  col- 
lected after  the  rain  has  fallen  for  a  time  sufficient  to  wash 
the  dust  from  the  air.  If  we  consider  the  cycle  of  water  in 
nature,  we  shall  understand  better  why  our  spring  and  river 
waters  must  contain  some  impurities. 

We  know  that  if  a  pan  of  water  is  allowed  to  stand  exposed 
to  the  action  of  the  air  and  the  sun,  the  water  disappears. 
Where  has  it-gone?  Since  it  does  not  disappear  when  in  a 
closed  vessel,  it  is  inferred  that  it  must  have  passed  into  the 
air.  It  is  not  visible,  but  exists  in  the  form  of  an  invisible 
vapor.  We  say  that  the  water  has  evaporated,  and  we  call 
the  change  evaporation. 

This  same  evaporation  occurs  on  a  large  scale  at  the 
surface  of  the  ocean.  Sometimes  the  phrase,  "  the  sun  draws 
the  water,"  is  used.  This  is  not  exactly  true ;  we  should  say, 
"  the  water  evaporates."  The  resulting  water  vapor  mixes 
with  the  air.  A  given  quantity  of  air  cannot  hold  more 
than  a  certain  amount  of  water  vapor,  the  exact  amount 
depending  upon  the  temperature.  The  higher  the  tempera- 
ture of  the  air,  the  more  water  vapor  it  can  hold. 

The  air  over  the  ocean  absorbs  the  water  vapor  wrhich 
rises  from  it.  The  air,  laden  with  water  vapor,  may  be 
blown  inland.  When  the  air  cools,  it  cannot  hold  as  much 
water  and  so  some  of  it  condenses  and  forms  clouds.  Fog 
and  mist  are  due  to  the  same  cause,  and  are  really  low  clouds. 
This  condensation  continues  until  the  drops  of  water  become 
so  large  that  they  fall  as  rain.  Before  it  can  rain,  then, 
it  is  necessary  that  the  air  contain  water  vapor,  and  that 


WATER 


19 


this  air  be  cooled.     This  explains  why  certain  regions  have 
more  or  less  rainfall  than  others. 

The  water  cycle.  The  rain,  in  falling  through  the  air, 
dissolves  certain  gases  from  it,  and  washes  out  the  dust. 
Notice  how  dirty  the  first  rain  water  that  falls  is,  especially 
in  the  city.  The  amount  of  water  that  falls  each  year 
in  the  form  of  rain  or  snow  is  very  great.  It  is  enough,  if  it 
were  equally  distributed,  and  fell  all  at  one  time,  to  make  a 


FIG.  6.  —  Water  table.     The  ground  is  saturated  with  water  below  the 
dotted  line. 

layer  about  three  feet  deep  over  all  the  land.     This  amounts 
to  about  30,000  cubic  miles  of  water. 

When  the  rain  strikes  the  ground,  a  portion  of  it  sinks  in, 
and  slowly  passes  through  the  soil,  until  it  meets  an  impervi- 
ous layer,  such  as  a  bed  of  clay.  Here  it  may  accumulate  and 
saturate  the  soil  for  some  distance  above  the  clay.  This 
reservoir  of  water  contained  in  the  ground  is  called  ground 
water.  It  is  this  ground  water  that  supplies  water  to  wells. 
The  upper  surface  of  the  saturated  soil  is  called  the  water 
table.  This  is  not  necessarily  level,  but  may  have  a  gentle 
slope.  In  case  this  water  table  rises  as  high  as  the  surface  of 
the  ground,  a  spring,  pond,  lake,  or  stream  is  formed  (Fig.  6). 


WEED    CHEMISTRY 


20 


CHEMISTRY   IN  THE   HOME 


The  height  of  the  water  table  varies  with  the  amount  of 
rainfall,  and  hence,  during  very  dry  seasons,  it  may  become  so 
low  that  springs,  and  even  streams,  may  dry  up  and  cease  to 
run.  The  spring  water  flows  into  a  brook,  the  brook  into 
a  river,  and  the  river  into  the  ocean.  Thus  the  water  cycle  is 
completed.  The  water  came  from,  and  returns  to,  the  ocean, 
and  this  continues  over  and  over  again. 

How  water  becomes  impure.  In  passing  through  the 
ground,  the  water  dissolves  any  soluble  matter  that  may  be 


FIG.  7.  —  Contamination  of  well  water. 

present,  and  thus  becomes  somewhat  impure.  Most  of  these 
impurities  are  harmless,  but  if  the  water  comes  in  contact 
with  sewage,  it  may  be  so  contaminated  as  to  be  dangerous 


WATER 


21 


to  drink  (Fig.  7).  It  can  usually  be  made  safe  by  boiling, 
and  this  is  a  wise  precaution  to  take,  in  case  there  is  doubt 
as  to  the  purity  of  the  water. 

Distilling  water.  The  commercial  purification  of  water  is 
usually  accomplished  by  distilling  it.  The  water  to  be  purified 
is  placed  in  a  vessel  (still),  closed  at  the  top,  and  provided 
with  only  one  escape  pipe.  The  water  is  heated  to  the  boil- 
ing point.  Most  of  the  impurities,  such  as  salt  and  calcium 
sulphate,  are  not  vola- 
tile, and  so  remain  in 
the  still.  Many  of 
you  have  noticed  the 
crust  that  is  formed 
on  the  inside  of  the 
tea-kettle.  This  is  the 
result  of  the  evapo- 
ration of  the  water, 
leaving  the  dissolved 
matters  behind.  The 
water  in  the  still 
(A,  Fig.  8)  changes  into  steam,  and  this  steam  passes  through, 
the  escape  pipe,  which  is  surrounded  with  cool  water  in  the 
condenser  C.  Cooling  the  steam  condenses  it,  and  pure 
water  drops  from  the  end  of  the  pipe  into  D.  This  distilled 
water  will  not  be  perfectly  pure,  as  it  still  contains  some  dis- 
solved gases,  but  it  is  so  nearly  pure,  that  it  is  used  in  the 
laboratory  for  chemical  work. 

This  same  process,  distillation,  is  used  to  separate  two 
-liquids  having  different  boiling  points.  Alcohol,  when  it  is 
made,  is  a  very  dilute  solution  of  alcohol  in  water.  This 
mixture  is  distilled,  and  as  alcohol  has  a  lower  boiling  point 
than  water,  173°  F.,  it  boils  first,  and  on  condensing  the 


FIG.  8.  —  Distillation  of  water. 


22 


CHEMISTRY   IN  THE  HOME 


vapor,  alcohol  containing  only  a  small  percentage  of  water  is 
obtained.  This  process,  called  fractional  distillation,  is  also 
used  to  separate  crude  petroleum,  as  it  is  pumped  from  the 
earth,  into  gasoline,  naphtha,  kerosene,  and  lubricating  oils. 
Purifying  water.  Water  as  it  comes  from  the  ground  often 
contains  suspended  matter.  This  is  especially  true  of  the 
waters  of  the  western  rivers.  This  suspended  matter  may 
be  removed  by  filtration,  or  by  allowing  the  water  to  stand 
until  the  suspended  matter  has  settled.  The  water  supply 
of  cities  must  sometimes  be  taken 
from  muddy  rivers.  It  may  be 
cleared  by  filtering  it  through  large 
beds  of  sand.  This  removes  the 
suspended  matter,  but  does  not 
remove  the  bacteria,  nor  the  dis- 
solved matter. 

Composition  of  water.  Water  was 
long  thought  to  be  an  element,  that 
is,  a  substance  so  simple  in  its  com- 
position that  it  could  not  be  broken 
up  into  other  substances.  We  now 
know  that  this  is  not  true,  but  that 
water  is  composed  of  two  gases  com- 
bined chemically. 

We  determine  its  exact  composi- 
tion by  means  of  electrolysis.  Pure 
water  will  not  conduct  the  electric 
current,  but  if  a  little  sulphuric  acid 

is  added>  it:  allows  the  current  to 
pass.  This  acidulated  water  is 
placed  in  a  U-shaped  tube,  so  arranged  that  an  electric 
current  can  be  sent  through  the  water.  The  electricity 


WATER  23 

breaks  up  the  water  particles,  and  two  gases  are  set  free, 
one  in  each  arm  of  the  U  tube  (Fig.  9).  There  is  twice  as 
much  of  one  gas  as  of  the  other. 

The  gas  present  in  the  larger  volume  is  named  hydrogen, 
and  is  noteworthy  because  it  is  the  lightest  gas  known,  and 
because  it  burns  with  an  exceedingly  hot  flame.  The  other 
gas,  oxygen,  is  one  of  the  gases  contained  in  the  air,  and  it 
is  essential  to  life. 

When  we  pull  any  substance  apart  in  order  to  find  out 
its  composition,  we  call  the  operation  analysis.  By  pass- 
ing the  electric  current  through  the  water,  we  analyze  it, 
and  find  its  composition  by  volume  to  be  two  volumes  of 
hydrogen  to  one  volume  of  oxygen.  , 

Elements.  Chemists  have  analyzed  many  thousands  of 
different  substances  to  find  of  what  they  are  composed.  The 
results  are  somewhat  surprising.  They  show  us  that  all  the 
materials  that  form  our  world  are  made  up  of  only  about  83 
different  kinds  of  matter,  and  that  by  combining  these  in 
different  proportions,  we  may  make  all  of  the  various  sub- 
stances that  we  know.  Thus,  sugar  is  found  to  contain  three 
different  kinds  of  matter,  that  is,  three  elements.  They  are 
oxygen  and  hydrogen,  the  elements  that  we  found  in  water, 
and  carbon,  which  is  the  name  chemists  give  to  the  black 
material  in  coal. 

Occasionally  a  new  element  is  found.  Radium  is  an  ex- 
ample of  this.  It  was  discovered  in  1898  by  Madame  Curie. 

Notice  that  the  definition  of  element  is  not  a  substance 
that  cannot  be,  but  a  substance  that  has  not  been  decomposed 
into  simpler  substances.  In  the  past,  materials  have  been 
thought  to  be  elements,  that  later  have  been  decomposed.  Of 
the  83  elements  known  we  shall  study  only  a  few  of  the  more 
common  ones,  as  oxygen,  hydrogen,  chlorine,  iron,  and  sodium. 


24  CHEMISTRY  IN  THE  HOME 

Compounds  and  mixtures.  When  elements  combine  to 
form  pure,  definite  substances,  we  call  them  compounds. 
Sugar,  salt,  and  starch  are  examples.  If  elements  or  com- 
pounds are  mixed  together  without  any  chemical  change 
taking  place,  we  call  the  result  a  mixture.  Sea  sand  is  a 
mixture.  It  contains  sand,  salt,  seaweed,  etc.,  all  mixed 
together,  but  not  chemically  combined.  Muddy  water  is 
another  example.  The  mud  is  mechanically  mixed  with 
the  water,  and  can  be  separated  from  it  by  filtering. 

Law  of  Definite  Proportions.  One  distinction  between  a 
compound  and  a  mixture  is  that  the  composition  of  a  com- 
pound is  always  the  same,  while  the  composition  of  a  mixture 
may  vary  between  wide  limits.  Water  has  been  analyzed 
thousands  of  times  with  the  invariable  result  that  its  com- 
position is  always  found  to  be,  hydrogen  f ,  and  oxygen  ^,  by 
volume.  Water,  then,  must  be  a  compound,  for  we  cannot 
imagine  that  any  accidental  mixture  of  hydrogen  and  oxygen 
would  always  have  the  same  proportions. 

Brass  is  made  by  melting  together  zinc  and  copper.  On 
analyzing  different  specimens,  we  find  that  the  percentage 
of  zinc  varies  from  40%  to  75%.  Brass,  then,  must  be  a 
mixture  and  not  a  compound.  These  facts  give  us  the  Law 
of  Definite  Proportions,  which  may  be  stated  thus:  The 
composition  of  every  pure  chemical  compound  is  always  the 
same. 

Synthesis  of  water.  We  may  show  the  composition  of 
water  in  still  another  way.  If  we  mix  two  volumes  of  hydro- 
gen with  one  volume  of  oxygen,  put  the  mixture  in  a  glass 
tube,  one  end  of  which  is  closed,  set  the  open  end  in  a  dish 
of  mercury,  so  as  to  prevent  any  air  from  getting  in,  and  then 
set  fire  to  the  mixture,  the  gases  will  disappear,  and  a  few 
drops  of  water,  formed  by  the  combination  of  the  two  gases, 


WATER 


25 


will  appear  in  the  tube  (Fig.  10).     We  can  easily  set  fire 

to  the  gases  by  passing  an  electric  spark  between  the  points 

of     platinum     wires 

which  are  sealed  in 

the    glass    tube,    so 

that    their   ends   do 

not  quite  touch. 

The  formation  of 
water  in  this  way 
is  called  synthesis. 
Chemists  can  build 
up  in  such  ways  as 
this  a  great  many 
substances  that  na- 
ture makes  in  plants 
and  animals.  Thus 
we  have  synthetic 
indigo,  vanilla,  cam- 

'  FIG.  10.  —  Synthesis  of  water 

phor,  etc.    These  are 

not  imitations,  but  are  the  real  substances,  formed  by  man, 

instead  of  by  nature,  from  the  materials  of  which  they  are 

composed.     Often  such  synthetic  products  are  cheaper  than 

the  natural,  and  equally  good.     It  is,  of  course,  a  fraud  when 

they  are  sold  as  natural  products,  instead  of  being  marked 

synthetic. 

Composition  of  water  by  weight.  The  composition  of 
water  by  weight  can  easily  be  determined.  Oxygen  weighs, 
volume  for  volume,  sixteen  times  as  much  as  hydrogen. 
Since  water  is  composed  of  two  volumes  of  hydrogen  to  one 
of  oxygen,  its  composition  by  weight  must  be  two  of  hydrogen 
to  sixteen  of  oxygen,  or  one  of  hydrogen  to  eight  of  oxygen. 
That  is,  by  weight  water  is  ^  hydrogen  and  |  oxygen. 


26  CHEMISTRY   IN  THE  HOME 

SUMMARY 

Density  is  the  mass  per  unit  volume. 

Water  boils  at  212°  F.  and  freezes  at  32°F. 

The  composition  of  water  by  volume  is  one  of  oxygen  to  two  of 
hydrogen ;  by  weight,  eight  of  oxygen  to  one  of  hydrogen. 

An  element  is  a  substance  that  has  not  been  decomposed  into 
simpler  substances. 

A  compound  is  a  pure  substance  composed  of  elements  chemically 
combined. 

A  mechanical  mixture  is  a  substance  composed  of  two  or  more  in- 
gredients the  individual  particles  of  which  are  not  chemically 
combined,  but  exist  side  by  side. 

Analysis  is  the  pulling  apart  of  a  substance  to  find  out  of  what  it  is 
composed. 

Synthesis  is  the  formation  of  a  compound  from  the  elements  com- 
posing it. 

Electrolysis  is  analysis  brought  about  by  electricity. 

Law  of  Definite  Proportions :  The  composition  of  every  pure 
chemical  compound  is  always  the  same. 

Exercises 

1.  Is  distilled  water  free  from  all  impurities?     Explain. 

2.  Is  brass  an  element?     Explain. 

3.  Name  two  common  elements. 

4.  Is  a  lamb  chop  a  compound,  an  element,  or  a  mixture? 
Explain. 

5.  How  can  you  prove  that  wood  is  not  an  element  ? 

6.  Does  the  boiling  of  water  remove  the  impurities  ?  If  not,  why 
does  it  make  the  water  fit  to  drink? 

7.  How  would  you  distinguish  between  distilled  water  and 
perfectly  clear  colorless  spring  water  ? 

8.  Why  may  water  drawn  from  a  well  near  a  farmhouse  be 
clear,  and  still  unfit  for  drinking  purposes? 

9.  Is  synthetic  indigo  as  good  as  natural  indigo?     Explain. 
10.   Why  do  water  pipes  sometimes  burst  in  cold  weather  ? 


CHAPTER  III 
SOLUTION 

Solution  explained.  We  are  all  familiar  with  the  change 
that  takes  place  when  we  stir  sugar  in  our  coffee.  The  solid 
sugar  disappears,  the  tiny  particles  that  compose  it  being 
distributed  uniformly  throughout  the  coffee.  The  resulting 
liquid  we  call  a  solution  of  sugar. 

We  are  so  accustomed  to  seeing  and  thinking  of  matter  in 
large  masses,  that  we  do  not  realize  how  small  the  individual 
particles  are  that  make  up  these  masses.  A  bit  of  dye, 
aniline  violet,  as  large  as  the  head  of  a  pin,  will  distinctly 
color  five  gallons  of  water,  when  dissolved  in  it.  That  is, 
the  individual  particles  that  make  up  this  substance  are  so 
small,  that,  when  they  are  separated  from  each  other,  and 
mixed  with  the  water,  there  are  enough  of  them  present  in 
each  drop  of  the  five  gallons  to  give  it  a  distinct  color. 

Many  substances  when  mixed  with  water  behave  in  this 
way.  Their  particles  are  separated  from  each  other  and 
spread  uniformly  through  the  water,  and,  even  on  long 
standing,  these  particles  do  not  separate  from  the  water, 
but  remain  uniformly  mixed  with  it.  This  intimate,  uni- 
form, and  permanent  mixture  of  a  solid  and  a  liquid  we  call 
a  solution. 

Emulsions.  When  oil  and  water  are  shaken  together, 
they  mix,  but  on  standing  the  two  separate.  If,  however, 
some  mucilaginous  material  is  added  to  the  water,  it  seems 

27 


28  CHEMISTRY   IN   THE   HOME 

to  coat  over  the  small  globules  of  the  oil,  and  even  on  long 
standing  these  do  not  separate  from  the  water.  Cream 
and  milk  are  examples  of  such  mixtures.  We  call  them 
emulsions. 

Suspension  explained.  Other  substances  when  mixed 
with  water  behave  in  an  entirely  different  manner.  At  the 
seashore  you  have  doubtless  watched  the  waves  roll  in  on 
the  beach.  The  sand  mixes  with  the  water,  but  does  not 
dissolve  and  disappear.  Instead,  it  soon  settles,  and  the  sea 
water  is  once  more  clear.  We  cannot  produce  a  lasting  and 
uniform  mixture  of  sand  and  water. 

Muddy  water  is  an  example  of  the  same  thing.  Fine  soil 
from  the  ground  mixes  with  the  rain  water,  and  makes  it 
turbid.  It  will  not,  however,  remain  uniformly  mixed,  but, 
on  standing,  the  particles  of  soil  slowly  settle,  and  the  water 
becomes  once  more  clear.  The  time  required  for  the  particles 
of  soil  to  settle  depends  upon  the  size  of  these  particles.  If 
they  are  very  small,  it  may  take  days,  but  eventually  the 
soil  and  water  will  separate.  We  call  such  a  mixture  of  a 
liquid  with  the  relatively  coarse  particles  of  a  substance,  a 
suspension. 

The  same  liquid  is  often  both  a  solution  and  a  suspension. 
Coffee,  when  properly  made,  is  a  solution,  but  we  sometimes 
find  a  sediment  in  the  bottom  of  the  cup,  showing  that  the 
coffee  was  not  only  a  solution,  but  a  suspension  as  well,  and 
that,  on  standing,  some  of  the  fine  particles  have  settled. 

Solution  and  suspension  defined.  A  solid  is  in  solution  in 
a  liquid  when  the  particles  of  the  solid  are  uniformly  and  per- 
manently scattered  through  the  liquid,  while  a  solid  is  in 
suspension  in  a  liquid  when  its  particles  in  a  finely  divided 
state  are  mixed  with  a  liquid,  but  the  mixture  will  not  re- 
main a  uniform  one.  Before  reaching  the  end  of  the  chap- 


SOLUTION  29 

ter,  however,  we  shall  see  that  these  definitions  need  to 
be  somewhat  modified. 

Filtration.  To  distinguish  between  a  solution  and  a 
suspension,  the  easiest  way  is  to  strain,  or,  as  chemists  say, 
filter  it.  In  the  laboratory  we  use  filter  paper  for  this  purpose. 
This  is  a  porous  paper  that  will  allow  water  and  dissolved 
particles  to  pass  through,  but  will  not  permit  the  small 
particles  of  suspended  matter  to  pass.  If  we  pour  muddy 
water  through  such  a  paper,  the  sediment  will  be  held 
back,  while  the  clear  water  passes  through.  The  clear 
liquid  that  runs  through  is  the  filtrate,  while  the  solid 
matter  left  on  the  paper  is  the  residue.  In  the  home,  a 
number  of  thicknesses  of  finely  woven  cloth  will  serve  the 
same  purpose. 

Many  of  the  water  filters  that  screw  on  to  water  faucets 
contain  charcoal,  and  the  water  passing  through  its  fine  pores 
is  filtered.  Do  not  forget,  however,  in  using  such  filters, 
that  the  dirt  removed  from  the  water  remains  in  the  filter, 
and  that  the  filter  should  be  frequently  cleaned. 

In  some  water  filters  made  of  earthenware,  the  pores  of 
the  filter  are  so  fine  that  even  bacteria  are  kept  back.  The 
finer  the  pores,  the  more  thoroughly  the  filter  acts,  but  also 
the  more  slowly  the  liquid  passes  through,  so  we  must  use 
discretion  in  selecting  filters.  The  larger  the  pores,  the 
better,  so  long  as  they  are  small  enough  to  retain  particles 
of  the  size  we  wish  to  filter  out.  To  remove  cranberry  seeds 
and  skins  from  the  cooked  mass,  a  fine  cheesecloth  is  suffi- 
cient, while,  to  filter  muddy  water,  a  very  much  finer  filter 
is  necessary. 

Naming  different  kinds  of  solutions.  There  is  a  limit  to 
the  amount  of  a  substance  that  will  dissolve  in  a  liquid.  If 
we  add  a  little  granulated  sugar  to  a  test  tube  full  of  water, 


30  CHEMISTRY   IN   THE    HOME 

and  shake,  the  sugar  disappears.  It  has  dissolved,  and  we 
obtain  a  clear  solution.  If  we  then  add  a  second  small  por- 
tion of  sugar,  and  shake,  it  also  dissolves.  If,  however,  we 
continue  to  add  sugar,  shaking  after  each  addition,  we  at 
last  come  to  a  point  where  it  will  no  longer  dissolve,  but 
remains  in  the  bottom  of  the  test  tube.  We  call  such  a 
solution,  a  saturated  solution  at  that  temperature.  The 
water  has  then  dissolved  all  of  the  sugar  that  it  can.  If, 
however,  we  warm  the  test  tube,  the  excess  of  sugar  in  the 
bottom  will  dissolve.  As  we  again  add  more  sugar,  we  find 
that  it  also  will  dissolve,  that  is,  the  solution  is  no  longer 
saturated.  We  must  again  add  a  considerable  amount  of 
sugar,  to  produce  the  condition  in  which  some  remains  in 
the  bottom  of  the  test  tube,  that  is,  to  saturate  the  solution 
at  the  higher  temperature.  On  cooling,  the  solution  will  de- 
posit sugar  crystals,  similar  to  rock  candy,  until  the  cooled 
solution  contains  the  same  amount  of  sugar  that  it  did  before 
heating. 

It  is  generally  true  that  hot  water  will  dissolve  more  of  a 
solid  than  cold  water.  It  is  not  enough,  in  speaking  of  a 
saturated  solution,  to  say  simply  that  it  is  saturated;  we 
must  also  state  the  temperature.  A  saturated  solution  of 
alum  contains  only  5  parts  of  alum  in  100  parts  of  water 
at  32°  F.,  while  at  190°  F.  it  contains  over  200  parts  in  100. 

When  a  solution  is  nearly  but  not  quite  saturated,  we  call 
it  a  concentrated  solution.  If  it  contains  somewhat  less  of 
the  dissolved  substance,  it  is  called  strong,  while,  if  it  contains 
only  a  little,  we  speak  of  it  as  weak  or  dilute. 

A  tincture  is  a  solution  in  alcohol,  such  as  tincture  of  iodine. 
Vanilla  and  lemon  extracts  are  tinctures. 

It  is  awkward  to  have  to  speak  continually  of  the  "  dis- 
solved substance."  We  therefore  give  this  a  name ;  it  is  called 


SOLUTION  31 

the  solute,  while  the  liquid  that  dissolves  it  is  called  the 
solvent.  We  speak  of  their  mixture  as  a  solution.  Thus, 
our  sirup  of  sugar  is  a  solution,  the  sugar  is  the  solute,  and 
the  water  is  the  solvent. 

When  nothing  is  said  as  to  the  nature  of  the  solvent,  it  is 
understood  that  water  is  meant.  Other  solvents  such  as 
ether,  alcohol,  gasoline,  etc.,  are  often  used  when  the  sub- 
stance is  not  soluble  in  water.  For  instance,  grease,  which 
is  not  soluble  in  water,  dissolves  in  gasoline. 

Solutions  of  liquids.  Not  only  solids,  but  many  liquids,  are 
soluble  in  liquids.  When  we  buy  alcohol  it  is  often  labeled 
95%.  This  means  that  95%  of  the  liquid  is  alcohol,  and  5% 
water.  The  water,  a  liquid,  has  dissolved  in  alcohol,  another 
liquid.  In  this  particular  case,  alcohol  and  water  mix  in  all 
proportions,  that  is,  we  cannot  have  a  saturated  solution  of 
alcohol  in  water.  When  this  is  the  case,  we  call  the  liquids 
miscible.  Usually,  however,  with  liquids,  as  with  solids,  only 
a  certain  amount  of  one  liquid  will  dissolve  in  another.  We 
may  therefore  have  a  saturated  solution  of  one  liquid  in 
another,  as  ether  in  water. 

Solutions  of  gases.  That  liquids  can  dissolve  gases,  is 
shown  by  what  happens  when  a  glass  of  cold  water  stands  for 
some  time  in  a  warm  room.  You  know  that  the  inside  of 
the  glass  becomes  covered  over  with  tiny  bubbles  of  some 
gas.  Knowing  as  you  do  that  fish  require  air  to  live,  it  is 
easy  to  guess  that  this  gas  is  air  that  has  been  dissolved  in 
the  water.  Evidently,  gases  do  not  behave  as  solids  do, 
for  warming  the  water  has  decreased  its  ability  to  dissolve 
air,  and  so  the  air  forms  bubbles  on  the  glass. 

The  ammonia  water  that  you  use  for  cleaning  purposes  is 
a  solution  of  ammonia  gas  in  water.  Why  does  the  cork  of 
the  ammonia  bottle  sometimes  fly  out  on  hot  days?  Soda 


32  CHEMISTRY   IN   THE   HOME 

water  is  another  common  example  of  a  gas  dissolved  in  water. 
Remember  that,  while  heating  generally  increases  the  solubil- 
ity of  solids  in  liquids,  it  decreases  the  solubility  of  gases  in 
liquids. 

Effect  of  pressure  on  solubility  of  gases.  The  next  time 
you  draw  a  glass  of  vichy  or  seltzer  from  a  siphon,  notice  that 
the  liquid  inside  the  siphon  fills  with  gas  bubbles,  and  that  on 
standing  these  disappear.  This  is  because  the  solubility  of 
a  gas  in  a  liquid  is  dependent  not  only  upon  the  temperature, 
but  upon  the  pressure.  When  we  draw  from  the  siphon,  we 
diminish  the  pressure  inside.  This  decreases  the  solubility 
of  the  gas,  and  gas  bubbles  form.  This  goes  on  until  enough 
gas  has  escaped  so  that  the  water  is  saturated  at  the  new 
pressure,  when  the  water  once  more  becomes  clear.  Roughly, 
doubling  the  pressure  doubles  the  solubility  of  a  gas  in  a 
liquid. 

Many  gases  are  very  soluble  in  water.  Ammonia  gas  is 
so  soluble  in  water,  that  more  than  700  quarts  of1  it  will 
dissolve  in  one  quart  of  water  at  ordinary  room  tempera- 
ture. 

Solution  not  limited  to  solids.  You  know  that  air  will 
dissolve  water,  because  if  a  pan  of  water  is  exposed  to  the 
air,  the  water  disappears.  Water  will  also  dissolve  air,  for 
it  is  this  dissolved  air  that  fish  breathe.  You  are  also  familiar 
with  cases  of  solids  and  liquids  dissolving  in  liquids.  Gases 
also  dissolve  in  solids,  as  we  shall  find  later  in  our  work.  We 
must  then  not  limit  our  use  of  the  word  solution  to  the  case 
of  solids  dissolving  in  liquids,  but  we  must  think  of  solids, 
liquids,  and  gases  as  being  all  soluble  in  other  solids,  liquids, 
or  gases.  This  of  course  does  not  mean  that  every  gas, 
liquid,  or  solid  is  soluble  in  every  other  gas,  liquid,  or  solid, 
but  certain  ones  are  soluble  in  certain  others. 


SOLUTION 


33 


Crystallization.  When  a  saturated  solution  is  allowed  to 
stand,  exposed  to  the  air,  some  of  the  solvent  evaporates, 
and  the  solute  is  deposited  in  the  dish  in  the  form  of  crystals, 
that  is,  in  the  form  of  some  geometrical  solid,  bounded  by 
plane  surfaces. 


FIG.  11.  —  Crystals,     a,  rock  candy;  b,  snow;  c,  washing  soda. 

At  the  first  opportunity,  examine  some  rock  candy.  You 
will  find  that  the  pieces  of  sugar  have  a  definite  shape,  and 
that  each  resembles  its  neighbor  (Fig.  11,  a). 

You  may  have  noticed  the  regularity  of  form  of  snow  and 
frost  crystals  (Fig.  11,  6).  If  you  have  not,  at  the  next 
snowfall,  catch  a  few  flakes  of  snow  on  a  black  cloth  and 


34  CHEMISTRY   IN   THE    HOME 

examine  them  under  a  reading  glass.  The  crystals  may  then 
be  distinctly  seen. 

There  are  many  substances,  such  as  ice,  that  are  crystal- 
line, that  is,  composed  of  crystals.  These  may  be  so  crowded 
together  that  distinct  separate  crystals  cannot  be  seen.  When 
we  separate  crystals  that  have  formed  in  a  liquid  from 
the  liquid  and  dry  them,  a  substance  comparatively  free 
from  impurities,  is  obtained.  Crystallization  is  often  used 
to  purify  compounds. 

Examine  some  salt  at  home  with  a  small  magnifying  glass. 
You  will  find  that  you  can  make  out  the  shape  of  its  crystals 
without  difficulty.  The  crystals  of  different  substances  have 
different  shapes,  and  it  is  often  possible  to  identify  a  sub- 
stance by  the  shape  of  its  crystals.  Not  all  substances 
crystallize.  Flour  does  not.  We  call  such  a  substance 
amorphous. 

Water  of  crystallization.  Occasionally,  crystals  in  form- 
ing from  solution  combine  with  water.  Common  washing 
soda  is  an  example  of  this  (Fig.  ll,c).  If  you  place  a  dry 
crystal  of  washing  soda  in  a  test  tube  and  heat  it,  a  large 
amount  of  water  is  given  off,  and  a  white  powder  remains  in 
the  bottom  of  the  test  tube.  In  this  particular  case,  106 
pounds  of  washing  soda  will  combine  with  180  pounds  of 
water,  to  form  286  pounds  of  crystalline  washing  soda. 
That  is,  more  than  half  of  the  crystal  is  water.  This  water 
which  is  not  mechanically  mixed  with,  but  chemically  com- 
bined with,  the  washing  soda,  is  called  water  of  crystallization,. 

Efflorescent,  deliquescent,  and  hygroscopic  substances. 
If  crystals  of'  washing  soda  are  allowed  to  stand  in  the  air, 
they  give  up  this  water  of  crystallization,  and  fall  to  a  white 
powder.  This  is  called  efflorescence.  Only  a  few  of  the  com- 
pounds containing  water  of  crystallization  are  efflorescent. 


SOLUTION  35 

Soda  lye,  or,  as  chemists  name  it,  sodium  hydroxide,  be- 
haves in  quite  a  different  manner.  If  a  lump  of  this  com- 
pound is  exposed  to  the  air,  it  absorbs  water  from  the  air, 
and  becomes  a  solution.  This  is  called  deliquescence. 

Many  substances  that  are  not  deliquescent  will  absorb  a 
little  water.  If  paper  is  dried,  weighed,  exposed  to  the  air, 
and  weighed  again,  it  will  be  found  to  have  absorbed  about 
10%  of  water.  We  cannot  call  paper  deliquescent,  because 
it  will  not  go  on  absorbing  water  until  it  dissolves.  Instead, 
we  call  it  hygroscopic.  Cloth,  wood,  and  leather  are  all 
hygroscopic. 

Supersaturated  solutions.  If  vinegar,  or,  as  chemists 
name  it,  acetic  acid,  acts  on  washing  soda,  a  chemical  change 
takes  place  and  a  new  substance,  sodium  acetate,  is  formed. 
This  substance  is  readily  soluble  in  water,  but  its  solution 
shows  certain  peculiarities. 

If  we  prepare  a  cold  saturated  solution  of  sodium  acetate, 
add  a  large  excess  of  the  solid,  and  heat,  the  solid  all  dis- 
solves. On  cooling,  you  would  naturally  expect  that  the 
excess  of  sodium  acetate  would  crystallize,  and  that  we  would 
again  obtain  a  cold  saturated  solution  mixed  with  crystals. 
Most  substances  do  act  in  this  way,  but  sodium  acetate  so- 
lution on  cooling  behaves  differently,  since  no  solid  separates. 
By  preparing  a  hot  concentrated  solution  and  then  cooling, 
we  have  obtained  a  solution  that  contains  many  times  as 
much  sodium  acetate  dissolved  as  we  could  have  dissolved 
by  merely  shaking  the  solid  with  cold  water.  Such  a  solution 
is  called  supersaturated. 

A  supersaturated  solution  will  remain  in  a  fluid  condition, 
if  put  in  a  flask  and  corked,  until  a  crystal  of  the  solute  is 
dropped  into  it.  Then  the  excess  of  the  solute  over  that 
required  to  form  an  ordinary  saturated  solution  crystallizes, 

WEED    CHEMISTRY 3 


36  CHEMISTRY   IN   THE   HOME 

and  an  ordinary  saturated  solution,  containing  crystals  of 
the  solute,  results.  During  the  process  of  crystallization 
much  heat  is  given  out,  and  the  temperature  of  the  solution 
rises.  A  number  of  substances  form  supersaturated  solu- 
tions, among  others  the  "  hypo  "  of  the  photographer. 

Self -heating  hot  water  bottle.  Advantage  has  been  taken 
of  supersaturated  solutions  to  prepare  a  hot  water  bag  that 
can  be  used  at  any  time  without  requiring  hot  water.  A 
rubber  bag  is  filled  with  a  supersaturated  solution,  which,  so 
long  as  it  remains  corked,  will  remain  fluid.  When  we  wish  to 
use  the  bag,  we  take  out  the  cork,  blow  upon  it  to  evaporate 
the  water,  thus  obtaining  a  thin  film  of  crystals  upon  the 
cork,  and  then  replace  the  cork.  Crystallization  then  takes 
place  and  the  mass  becomes  warm.  The  bag  can  then  be  used 
as  any  other  hot  water  bag  would  be.  Before  using  again,  the 
rubber  bag,  corked,  is  placed  in  hot  water  until  all  of  the 
crystals  have  dissolved.  It  is  necessary  to  be  sure  that  every 
crystal,  no  matter  how  small,  has  dissolved,  as  otherwise  the 
supersaturated  solution  would  again  crystallize  as  the  fluid 
cools.  Such  bags  are  not  in  common  use  because  hot  water 
is  so  easily  available. 

You  can  easily  prepare  such  a  device  for  home  use,  using 
a  bottle  containing  a  supersaturated  solution  of  "  hypo,"  or, 
as  it  is  correctly  named,  sodium  thiosulphate.  To  prepare 
such  a  solution,  dissolve  a  pound  of  hypo  in  a  half  ounce  of 
boiling  water.  If  the  solution  is  not  perfectly  clear,  filter 
it  through  absorbent  cotton,  pour  the  liquid  into  a  pint  jar, 
and  seal  tightly. 

SUMMARY 

A  solution  is  a  uniform  mixture  of  substances  which  do  not  separate 

even  on  long  standing. 
A  suspension  is  a  mixture  of  substances  that  separate  on  standing. 


SOLUTION  37 

Defining  the  parts  of  a  solution.  The  solute  is  the  substance  dis- 
solved ;  the  solvent  the  material  in  which  the  solute  dissolves ; 
and  a  solution  is  the  result. 

Strength  of  a  solution.  A  saturated  solution  is  one  containing  as 
much  of  the  solute  as  will  dissolve  at  the  given  temperature. 
A  concentrated  solution  is  one  not  quite  saturated.  A  dilute 
solution  is  a  weak  solution. 

A  tincture  is  a  solution  in  alcohol. 

The  filtrate  is  the  clear  liquid  that  passes  through  the  filter  paper. 

Miscible  liquids.  When  one  liquid  will  dissolve  in  another  in  any 
proportion,  the  liquids  are  miscible. 

A  crystal  is  a  natural  geometrical  solid  bounded  by  plane  surfaces. 

Water  of  crystallization  is  water  chemically  combined  in  a  crystal. 

An  efflorescent  substance  gives  up  its  water  of  crystallization  to  the 
air,  without  being  heated. 

A  deliquescent  substance  absorbs  water  from  the  air,  finally  dis- 
solving in  it. 

A  hygroscopic  substance  absorbs  a  limited  amount  of  water  from 
the  air  but  does  not  form  a  solution. 

Heat  and  solubility.  Heating  generally  increases  the  solubility  of 
solids  and  decreases  the  solubility  of  gases  in  liquids. 

Exercises 

1.  Is  a  cup  of  tea  a  solution  or  a  suspension  ?     Explain. 

2.  Why  does  dipping  a  greasy  waist  in  gasoline  clean  it? 

3.  Why  does  alcohol  clean  eyeglasses  better  than  water? 

4.  How  would  you  test  silk,  to  find  out  if  it  is  hygroscopic? 

5.  In  buying  washing  soda,  is  it  well  to  insist  on  having  clear 
glassy  crystals?     Explain. 

6.  Why  is  soda  lye  put  up  in  soldered  tin  cans? 

7.  Name  three  natural  crystals  with  which  you  are  familiar. 

8.  Name  three 'amorphous  substances. 

9.  Is  ice  crystalline  ?    Explain. 


CHAPTER  IV 
OXYGEN   AND   HYDROGEN   PEROXIDE 

Occurrence  of  oxygen.  From  the  study  of  water  you  know 
something  of  the  properties  of  oxygen,  and  of  the  great  im- 
portance of  this  element  to  life.  Oxygen  is  found  every- 
where. Water  is  by  weight  -|  oxygen;  our  bodies  are  f 
oxygen;  sand  is  J  oxygen;  while  marble,  washing  soda, 
vinegar,  meats,  and  vegetables  contain  it  in  considerable 
proportion. 

That  compounds  containing  oxygen  should  be  so  widely 
distributed  is  natural.  You  will  remember  the  action  of 
the  air  on  various  substances.  The  rusting  of  metals,  the 
decay  of  wood,  and  the  spoiling  of  foods,  all  result  in  the 
formation  of  oxygen  compounds.  These  changes  have  always 
been  going  on,  and,  as  a  result,  large  amounts  of  such  oxygen 
compounds  now  exist  everywhere.  It  is  estimated  that  50  % 
of  the  earth's  crust  is  oxygen. 

Methods  of  preparing  oxygen.  You  have  already  learned 
that  the  decomposition  of  water  by  electricity  yields  oxygen. 
But  when  we  wish  to  obtain  it  in  considerable  amounts  in 
the  laboratory,  we  resort  to  another  method,  the  heating  of 
potassium  chlorate.  This  white  crystalline  compound,  that 
you  may  have  used  in  the  form  of  tablets  for  the  throat, 
contains  39%  of  oxygen,  all  of  which  it  gives  off  on  being 
heated.  It  has  been  found  that  the  addition  of  another  sub- 
stance, manganese  dioxide,  causes  the  potassium  chlorate  to 

38 


OXYGEN  AND  HYDROGEN  PEROXIDE 


39 


decompose  at  a  lower  temperature.  We  therefore  use  a 
mixture  of  these  two  substances  in  preparing  the  gas. 

A  mixture  of  three  parts  of  potassium  chlorate,  and  one 
part  of  manganese  dioxide,  is  placed  in  a  test  tube  (Fig  12) 
provided  with  a  cork  and  a  delivery  tube,  and  the  end  of  the 
delivery  tube  placed  under  water  in  a  pneumatic  trough. 
When  the  mixture  in  the  test  tube  is  heated,  it  decomposes. 
A  gas  passes  off  through  the  delivery  tube  and,  bubbling 
through  the  water,  escapes  into  the  air.  The  gas  which  first 
escapes  is  the  air  that 
was  in  the  test  tube. 
As  soon  as  all  the  air 
has  been  driven  off, 
the  gas  which  then 
escapes  is  oxygen.  If 
a  bottle  is  filled  with 
water  and  inverted 

FIG.  12.  —  Preparation  of  oxygen. 

over  the  end  of   the 

delivery  tube,  the  oxygen  will  displace  the  water,  and  will 
fill  the  bottle  with  pure  oxygen.  Many  gases  can  be  collected 
in  this  manner  over  water.  This  method  is  called  collec- 
tion by  displacement  of  water. 

Catalytic  agents.  After  all  the  oxygen  has  been  driven 
off,  water,  added  to  the  contents  of  the  flask,  dissolves  one 
of  the  residues.  If  the  mixture  is  filtered  and  the  filtrate  is 
evaporated,  a  white  solid  different  from  the  original  potas- 
sium chlorate  results.  It  is  called  potassium  chloride. 
Notice  carefully  the  difference  in  the  endings  of  the  names 
of  these  two  compounds. 

The  black  residue  on  the  filter  paper  is  the  manganese 
dioxide  originally  used.  It  has  undergone  no  change.  There 
are  many  such  cases  in  chemistry  where  we  add  a  substance 


40  CHEMISTRY  IN  THE  HOME 

for  the  purpose  of  aiding  or  checking  some  chemical  action, 
in  which  the  added  substance  does  not  itself  undergo  any 
permanent  change.  Such  an  action  is  called  a  catalytic 
action,  and  the  substance  added,  a  catalytic. agent. 

Properties  of  oxygen.  An  examination  of  the  oxygen  in 
the  bottle  shows  that  it  is  a  colorless,  odorless,  and  tasteless 
gas.  We  should  expect  this,  as  the  air  which  is  one  fifth 
oxygen  is  colorless,  odorless,  and  tasteless.  By  subjecting  it 
to  great  pressure  and  intense  cold,  it  can  be  changed  into  a 
pale  blue  liquid.  All  gases  can  be  liquefied  by  this  method. 
Oxygen  is  slightly  heavier  than  air  and  is  somewhat  soluble 
in  water,  4.1  volumes  of  oxygen  dissolving  in  a  hundred 
volumes  of  water  at  34°  F.  Fish  breathe  oxygen.  Were  it 
not  for  this  oxygen  in  solution,  they  would  drown. 

Oxides.  At  high  temperatures  oxygen  is  an  exceedingly 
active  element.  A  heated  piece  of  iron  burns  in  it,  and  most 
elements,  as  sulphur,  phosphorus,  carbon,  copper,  zinc,  and 
magnesium,  combine  directly  with  it.  These  compounds  of 
elements  with  oxygen  are  called  oxides,  and  are  very  common 
in  nature.  Water  might  be  called  an  oxide  of  hydrogen, 
while  sand  is  an  oxide  of  silicon. 

Oxidation  and  oxidizing  agents.  The  combining  of  oxygen 
with  any  substance  is  called  oxidation,  and,  if  the  combining 
is  accompanied  by  light  and  heat,  it  is  called  combustion. 
Substances  such  as  potassium  chlorate,  that  readily  cause 
oxidation,  are  called  oxidizing  agents.  If  you  throw  a  frag- 
ment of  charcoal  into  some  molten  potassium  chlorate,  it  will 
ignite  and  burn  furiously.  The  charcoal  is  oxidized  and 
the  potassium  chlorate  is  the  oxidizing  agent.  It  is  the  oxy- 
gen in  the  air  that  supports  burning  and  life. 

Oxygen  is  an  element  in  which  we  should  be  intensely 
interested,  for  our  existence  depends  upon  it.  It  is  the 


OXYGEN  AND  HYDROGEN  PEROXIDE  41 

oxygen  that  we  breathe  in  from  the  air  that  keeps  us  alive. 
Our  fires  burn  because  the  fuel  combines  with  the  oxygen 
of  the  air.  The  organic  waste  of  the  world  disappears  be- 
cause it  is  oxidized  by  oxygen.  There  is  perhaps  no  other 
element  that  we  use  so  continually. 

Ozone.  A  silent  electrical  discharge  is  found  to  change 
the  properties  of  oxygen  in  many  ways.  In  the  first  place 
three  volumes  of  oxygen  contract  to  form  two  volumes  of  a 
new  gas.  The  new  form  of  oxygen  thus  produced  is  called 
ozone.  It  is  a  gas  of  irritating  odor  and  is  an  active  form  of 
oxygen.  It  is  a  more  powerful  oxidizing  agent  than  oxygen. 
For  example,  silver  is  not  acted  upon  by  ordinary  oxygen  at 
any  temperature,  while  ozone  attacks  it,  forming  black  silver 
oxide.  Ozone  cannot  be  kept  for  any  considerable  length  of 
time,  as  it  slowly  turns  back  into  ordinary  oxygen.  A 
number  of  other  elements  also  exist  in  different  forms. 
Carbon,  for  example,  exists  as  the  diamond,  graphite  or  black 
lead,  and  lampblack.  All  these  different  forms  consist  only 
of  particles  of  carbon,  yet  the  physical  properties  of  the 
different  forms  are  dissimilar.  Such  forms  are  called  allo- 
tropic  modifications.  Ozone  is  such  an  allotropic  modification 
of  oxygen. 

Uses  of  ozone.  The  most  important  use  of  ozone  is  in 
the  purification  of  drinking  water.  When  used  in  the  proper 
concentration,  it  will  kill  any  number  of  bacteria,  and  attacks 
the  pathogenic  or  dangerous  germs  first.  The  German 
Imperial  Board  of  Health  has  shown  that  one  gram  of  ozone 
will  kill  30,000  cholera  bacteria  per  cubic  centimeter,  in 
250  gallons  of  water.  It  is  much  used  in  France  and 
Russia  to  purify  water. 

Ozone  does  not  kill  the  bacteria  when  used  to  ozonate  air, 
but  does  remove  the  odors  due  to  tobacco  smoke,  perspira- 


42  CHEMISTRY  IN  THE  HOME 

tion,  etc.  Owing  to  its  strong  oxidizing  power,  it  is  an  ideal 
bleaching  agent  for  oils,  but  its  high  cost  prevents  its  com- 
mercial use  for  this.  Owing  to  its  extreme  activity,  ozone 
is  a  poison,  and  must  be  used  with  care. 

Hydrogen  peroxide.  Like  many  other  elements,  hydrogen 
and  oxygen  combine  in  more  than  one  proportion.  In  water, 
one  part  of  hydrogen  unites  with  eight  parts  of  oxygen  by 
weight ;  in  hydrogen  peroxide,  one  part  of  hydrogen  unites 
with  sixteen  parts  of  oxygen  by  weight.  That  is,  for  every 
one  part  by  weight  of  hydrogen,  we  may  have  either  eight  or 
sixteen  parts  by  weight  of  oxygen.  You  will  notice  that 
these  two  numbers,  eight  and  sixteen,  are  in  the  simple  ratio 
of  1 :  2.  The  importance  of  this  fact  you  will  see  later,  when 
we  come  to  study  the  theory  of  chemistry.  This  new  com- 
pound, hydrogen  peroxide,  is  not  formed  by  the  direct  union 
of  the  elements.1 

Hydrogen  peroxide,  when  pure,  is  a  thick,  colorless  sirup, 
which  decomposes  easily.  It  is,  in  fact,  impossible  to  keep  it 
for  any  great  length  of  time,  as  it  decomposes,  giving  off  oxy- 
gen and  leaving  water.  This  makes  it  useful  as  an  oxidizing 
agent.  Whenever  it  is  mixed  with  anything  that  can  be 
easily  oxidized,  the  oxygen  combines  with  the  other  material 
and  destroys  it.  Thus,  if  hydrogen  peroxide  is  poured  on 
the  pus  in  a  wound,  the  pus  is  oxidized,  and  the  wound 
cleansed.  In  medicine  it  is  used  as  a  disinfectant  because  it 
leaves  only  water  as  a  residue.  A  3%  solution  of  it  in 
water  is  sold  under  various  names,  as  hydrogen  dioxide, 

1  The  commercial  way  of  preparing  hydrogen  peroxide  is  to  heat 
the  oxide  of  a  rare  metal,  barium,  until  it  has  taken  up  an  extra 
portion  of  oxygen,  forming  barium  peroxide.  Barium  peroxide  is 
then  mixed  with  cold,  dilute  sulphuric  acid.  The  barium  and 
hydrogen  exchange  places,  forming  barium  sulphate  and  hydrogen 
peroxide. 


OXYGEN  AND  HYDROGEN  PEROXIDE  43 

hydrogen  peroxide,  or  dioxygen.     It  is  a  safe  and   cheap 
home  remedy,  and  should  be  more  widely  used  than  it  is. 

Bleaching  power  of  hydrogen  peroxide.  Chemically,  it 
has  a  second  important  use.  There  are  many  substances 
that  need  to  be  bleached,  but  the  ordinary  bleaching  agents, 
as  chlorine,  are  so  powerful  that  they  not  only  bleach,  but 
attack  the  material  itself.  For  these  substances  hydrogen 
peroxide  is  an  excellent  bleach,  as  it  oxidizes  the  coloring 
matter  without  injuring  the  material  itself.  Silk,  wool,  and 
ivory  are  all  bleached  by  its  use. 

SUMMARY 
Oxygen  is  prepared  by  the  electrolysis  of  water,  or  by  heating  a 

mixture  of  potassium  chlorate  and  manganese  dioxide.     It  is  a 

colorless,  odorless,  tasteless  gas.     At  high  temperatures  it  is 

very  active,  combining  with  most  elements  to  form  oxides. 

It  supports  burning  and  life. 

An  oxide  is  a  combination  of  oxygen  with  one  other  element. 
Oxidation  is  the  combining  of  some  substance  with  oxygen. 
An  oxidizing  agent  is  a  substance  that  readily  gives  up  oxygen,  thus 

oxidizing  other  substances. 
A  catalytic  agent  is  a  substance  that  aids  chemical  change  without 

itself  being  permanently  changed. 

Ozone  is  an  active  form  of  oxygen  and  is  a  good  oxidizing  agent. 
Hydrogen  peroxide  is  a  good  oxidizing  agent,  and  because  of  this  is 

a  good  bleaching  agent  and  disinfectant. 

Exercises 

1.  Why  do  goldfish,  kept  in  a  glass  globe,  die  if  the  water  is  not 
often  changed? 

2.  If  oxygen  is  an  active  element,  why  does  not  the  coal  in  coal 
mines  burn  up? 

3.  Name  three  common  oxides  that  you  will  find  in  every  house. 

4.  Why  does  the  cork  of  a  hydrogen  peroxide  bottle  often  fly  out  ? 
6.   Why  is  the  cork  of  a  hydrogen  peroxide  bottle  bleached  ? 


CHAPTER  V 
HYDROGEN 

Occurrence  of  hydrogen.  Every  organism  is  made  up  of 
many  different  compounds.  One  element,  however,  exists 
in  practically  all  of  these  compounds,  namely,  hydrogen. 
It  is  found  combined  with  carbon  in  almost  every  organic 
compound.  Meat,  kerosene,  candles,  fats,  and  oils  all  con- 
tain it.  Hydrogen  is  found  free  in  nature  only  in  small 
quantities,  but  we  have  reason  to  believe  that  large  quantities 
exist  in  the  sun  and  stars.  Natural  gas,  rock  salt,  and  mete- 
orites all  .contain  it  in  small  quantities. 

Preparation  of  hydrogen.  To  prepare  hydrogen  we  may 
decompose  water  by  electricity,  or  by  the  action  of  certain 

metals  (as  sodium)  on  it ;  or, 
best  of  all,  we  may  obtain  it 
from  an  acid  by  the  action  of 
a  metal  upon  it.  Zinc,  for 
example,  is  placed  in  a  flask 
fitted  with  a  thistle  tube  and 
a  delivery  tube  (Fig.  13). 
Dilute  sulphuric  acid  is  added 
through  the  thistle  tube.  It 


FIG.  13.  —  Preparation  of  hydrogen. 


acts  upon  the  zinc,  forming 
zinc  sulphate  and  setting  hy- 
drogen free.  The  hydrogen  is  then  collected  by  water  dis- 
placement. Other  metals,  as  iron,  and  other  acids,  as 
hydrochloric  acid,  may  be  used  to  prepare  hydrogen. 

44 


HYDROGEN  45 

Properties  of  hydrogen.  -Hydrogen  is  a  tasteless,  odorless, 
colorless  gas.  It  can  be  condensed  to  a  liquid  under  high 
pressure  at  an  extremely  low  temperature.  It  is  the  lightest 
gas  known,  air  being  14.43  times  as  heavy  as  the  same  volume 
of  hydrogen.  It  burns  with  an  almost  colorless  flame,  giving 
an  intense  heat.  A  pound  of  hydrogen,  in  burning,  gives  out 
more  than  four  times  as  much  heat  as  a  pound  of  the  best 
coal.  It  is  therefore  a  most  excellent  fuel,  but  owing  to  its 
cost  and  bulk,  it  is  not  often  used  pure.  Mixed  with  other 
gases,  hydrogen  forms  illuminating  gas,  and  those  of  you 
who  have  gas  stoves  at  home  know  how  convenient  a 
fuel  that  is. 

The  lightness  of  hydrogen  is  made  use  of  in  balloons.  As 
air  weighs  14.43  times  as  much  as  hydrogen,  volume  for 
volume,  a  balloon  filled  with  hydrogen  will  lift  a  considera- 
ble weight.  The  German  military  balloons  are  filled  with 
hydrogen. 

Oxyhydrogen  blowpipe.  When  we  wish  an  especially 
intense  heat,  such  as  is  required  to  melt  platinum,  which  is 
one  of  the  exceedingly  infusible  metals,  we  resort  to  the 
oxyhydrogen  blowpipe 
(Fig.  14).  This  is 
a  device  consisting 
of  two  concentric 
tubes.  Through  the 

FIG.  14. —  Oxyhydrogen  blowpipe. 

outer  larger  one  hy- 
drogen is  forced,  and  through  the  inner  tube  oxygen. 
These  gases  are  both  used  under  pressure,  and  give,  when 
they  combine,  an  intensely  hot,  pointed  flame.  This  flame  is 
sometimes  used  to  produce  an  exceedingly  bright  light.  It 
is  itself  almost  invisible,  but  when  it  falls  upon  a  piece  of 
quicklime,  which  is  infusible  even  at  that  high  temperature, 


46 


CHEMISTRY   IN   THE    HOME 


the  lime  is  heated  to  incandescence  and  a  dazzling  bright 
light  results.  This  is  the  so-called  calcium  or  lime  light 
which  is  used  in  theaters  and  magic  lanterns  (Fig.  15).  It  is 

being  replaced,  how- 
ever, to  a  large  extent 
by  the  electric  light, 
which  is  brighter, 
cheaper,  and  more 
convenient. 

Hydrogen  a  reduc- 
ing agent.  The  ac- 
tion of  hydrogen  is, 
in  many  ways,  the 
reverse  of  that  of  oxygen.  If  we  heat  oxide  of  copper 
in  a  stream  of  dry  hydrogen,  the  hydrogen  will  combine 
with  the  oxygen,  forming  water,  and  leaving  metallic  copper 


U 


FIG.  15.  —  Burner  for  lime  light. 


FIG.  16.  —  Reduction  of  copper  oxide  by  hydrogen,  a,  hydrogen  generator ; 
b,  calcium  chloride  for  drying ;  c,  copper  oxide ;  <2,  anhydrous  copper 
sulphate. 

(Fig.  16).  Such  an  action  as  taking  away  oxygen  from 
a  compound  is  called  reduction.  It  is  evidently  the  reverse 
of  oxidation.  Hydrogen  is  then  a  reducing  agent,  and  is 


HYDROGEN  47 

largely  used  in  the  laboratory  for  that  purpose.  Car- 
bon is  another  excellent  reducing  agent,  and  is  used  com- 
mercially to  extract  metals  from  their  ores,  which  are  largely 
oxides.  Iron  is  made  in  enormous  quantities  by  this  process. 

SUMMARY 

Hydrogen  is  prepared  by  the  electrolysis  of  water,  by  the  action  of 
sodium  on  water,  or  by  the  action  of  a  metal  on  an  acid.  It  is  a 
colorless,  tasteless,  odorless  gas.  It  is  the  lightest  gas  known. 
It  burns  with  an  intense  heat.  It  is  a  good  reducing  agent. 

A  reducing  agent  is  a  substance  that  readily  takes  oxygen  away 
from  its  compounds. 

The  oxyhydrogen  blowpipe  is  used  to  produce  an  intense  heat. 

Exercises 

1.  How  can  you  prove  that  kerosene  contains  hydrogen? 

2.  Why  is  it  very  difficult  to  keep  hydrogen,  even  in  tightly 
corked  bottles  ? 

3.  Do  you  regard  a  mixture  of  hydrogen  and  oxygen  as  an  explo- 
sive ?    Explain. 

4.  One  should  never  apply  a  flame  to  apparatus  in  which  there  is 
hydrogen  without  testing  to  see  that  the  hydrogen  is  pure.     It  is  not 
safe  to  guess.     Why? 


CHAPTER  VI 
ATOMIC  THEORY 

The  alchemists.  All  through  the  Middle  Ages,  hundreds 
of  men,  called  alchemists,  worked  in  laboratories,  studying 
what  we  now  call  chemistry.  They  discovered  many  chem- 
ical compounds,  and  found  out  many  interesting  and  useful 
facts  about  them.  They  learned  how  to  make  sulphuric, 
hydrochloric,  and  nitric  acids;  how  to  extract  some  of  the 
metals,  as  zinc  and  lead,  from  their  ores ;  how  to  purify 
substances  by  distillation ;  in  short,  they  knew  and  used 
many  of  the  substances  and  operations  that  you  have  used  in 
your  work  in  chemistry.  Yet  they  knew  little  or  nothing  of 
what  we,  to-day,  call  the  science  of  chemistry.  This  was 
due  to  several  reasons.  They  were  not  trying  to  find  out  the 
laws  of  nature,  or  to  build  a  science,  but  to  learn  how  to 
transmute  base  metals  into  gold,  to  make  the  elixir  of  life, 
and  the  philosopher's  stone.  They  had  no  idea  of  the  use 
of  the  balance,  or  any  orderly  way  of  working.  They  made 
their  discoveries  by  mixing  substances  at  random,  and  then 
seeing  and  recording  what  happened.  Nor  was  one  man  will- 
ing to  help  others  by  publishing  what  he  had  found  out. 
They  learned  a  considerable  number  of  isolated  facts,  but 
failed  to  discover  those  laws  and  quantitative  relationships 
on  which  modern  chemistry  is  based. 

Chemistry  a  science.  It  was  not  until  the  time  of  the 
French  Revolution  that  chemists  realized  that  the  science  of 

48 


ATOMIC   THEORY  49 

chemistry  must  be  based  upon  knowing  not  only  what 
chemicals  are  used  in  chemical  changes,  but  how  much  of 
each,  the  weight  of  the  products  formed,  and,  most  important 
of  all,  the  laws  governing  these  changes.  It  was  at  this 
time  that  chemistry  first  really  became  a  science,  and  that 
chemical  facts  were  studied  with  the  aim  of  discovering  the 
laws  governing  them. 

Law  of  Definite  Proportions.  Just  as  soon  as  chemists 
began  not  only  to  pull  things  apart,  but  to  weigh  the  products 
obtained,  a  remarkable  fact  became  known.  It  was  found 
that  the  composition  of  every  chemical  compound  was  al- 
ways the  same.  Thus,  water  was  found  always  to  contain 
88. 8+  %  of  oxygen,  and  11.1+  %  of  hydrogen  by  weight. 
Or,  8  pounds  of  oxygen  always  combines  with  1  pound  of 
hydrogen,  to  produce  9  pounds  of  water.1  No  matter 
where  the  water  comes  from,  if  pure,  its  composition  is 
found  to  be  always  the  same.  Hundreds  of  other  com- 
pounds have  been  analyzed,  but  always  with  a  similar 
result.  If  a  substance  is  pure,  its  percentage  composition  is 
always  the  same ;  that  is,  a  compound  is  always  made  up  of 
the  same  elements  combined  in  the  same  proportion  by 
weight.  This  fact  has  come  to  be  called  the  Law  of  Definite 
Proportions,  and  may  be  stated  thus :  The  composition  of 
every  pure  chemical  compound  is  always  the  same. 

Law  of  Multiple  Proportions.  Soon  after  the  discovery  of 
the  Law  of  Definite  Proportions,  it  was  found  that  oxygen  and 
hydrogen  combined  not  only  in  the  proportion  of  8  to  1,  but 

1  It  must  be  remembered  that,  for  the  sake  of  clearness  in  these 
notes,  many  facts  are  stated  in  round  numbers.  Thus  oxygen  and 
hydrogen  really  combine  in  the  proportion  of  8  of  oxygen  to  1.008  of 
hydrogen.  The  exact  values  are  in  most  cases  given  in  the  tables 
in  the  appendix.  In  solving  problems,  the  approximate  values 
only  are  to  be  used. 


50  CHEMISTRY   IN   THE   HOME 

that  a  second  compound  existed  in  which  the  proportion  was 
16  to  1.  This  second  compound,  hydrogen  peroxide,  you 
have  already  studied.  You  will  notice  that  in  these  two 
compounds,  the  amounts  of  oxygen  that  combine  with  one 
pound  of  hydrogen,  namely,  8  to  16,  form  the  simple  ratio 
with  each  other  of  1  to  2. 

Compounds  of  many  other  elements  have  been  found  that 
show  this  same  fact.  Carbon,  for  example,  forms  two 
oxides.  We  can  combine  16  pounds  of  oxygen  with  12  pounds 
of  carbon,  forming  carbon  monoxide,  the  poisonous  gas 
found  in  our  illuminating  gas.  Or  we  can  combine  32  pounds 
of  oxygen  with  12  pounds  of  carbon,  forming  carbon  dioxide,, 
that  gaseous  substance  that  makes  soda  water  effervescent. 
That  is,  12  pounds  of  carbon  will  combine  with  either  16  or 
32  pounds  of  oxygen.  Here,  again,  you  will  notice  that  the 
amounts  of  oxygen  that  combine  with  the  same  amount  of 
carbon  form  a  simple  ratio,  1  to  2. 

The  same  fact  is  true  of  compounds  of  iron  with  sulphur, 
oxygen  with  nitrogen,  and  of  the  compounds  of  many  other 
elements.  From  these  facts  we  have  formulated  the  follow- 
ing Law  of  Multiple  Proportions :  //  two  elements,  A  and  B, 
combine  to  form  more  than  one  compound,  the  weights  of  the 
element  B  that  combine  with  a  fixed  weight  of  the  element  A, 
bear  a  simple  ratio  to  each  other. 

Matter  is  non-continuous.  Our  next  task  is  to  find  an 
explanation  as  to  why  these  laws  are  true.  There  are  only 
two  possibilities  as  to  the  constitution  of  matter.  Either 
matter  must  be  a  continuous  substance,  or  it  must  be  made  up 
of  small  particles  held  together  by  some  force.  Many  facts 
show  that  the  latter  view  is  the  correct  one.  To  the  eye,  a 
plate  of  iron  seems  to  be  a  continuous  solid.  We  know  that 
in  reality  it  is  not,  for  by  applying  an  enormous  pressure,  it  is 


ATOMIC   THEORY  51 

possible  to  force  water  through  the  solid  iron.  The  iron 
does  not  break,  yet  drops  of  water  find  their  way  through. 
This  must  be  because  the  iron  is  made  up  of  very  small 
particles,  and  the  water  finds  its  way  between  them,  showing 
not  only  that  the  iron  is  made  up  of  small  particles,  but  that 
these  small  particles  do  not  touch  each  other.  This  gives  us 
an  explanation  how  it  is  possible  for  a  bar  of  iron  to  expand 
when  heated  without  undergoing  any  change  in  weight. 
The  small  particles  that  compose  it  have  been  driven  further 
apart,  and  thus  occupy  more  room.  Cooling  and  hammering 
drives  them  closer  together,  and  so  the  bar  becomes  smaller, 
although  its  weight  does  not  change. 

Matter  is  made  up  of  small  particles.  If  we  mix  a  pint  of 
alcohol  with  a  pint  of  water,  we  naturally  expect  to  have  two 
pints  of  the  mixture.  Instead,  we  get  only  1.8  pints.  Evi- 
dently this  is  a  case  similar  to  the  mixing  of  a  pint  of  coffee 
beans  and  a  pint  of  granulated  sugar.  There  would  not  be  a 
quart  of  the  mixture,  as  the  sugar  sifts  in  between  the  larger 
coffee  beans.  In  the  same  way,  the  alcohol  and  water  being 
in  reality  made  up  of  tiny  particles,  and  these  particles  not 
filling  all  the  space,  the  smaller  particles  sift  in  between  the 
larger  ones,  thus  reducing  the  volume  of  the  mixture.  There 
are  just  as  many  particles  of  water  and  alcohol  as  before, 
only  the  space  between  them  has  diminished  and  therefore 
the  volume  has  become  less.  The  weight  of  course  remains 
unchanged.  It  is  impossible  to  explain  such  facts  as  these 
except  by  believing  that  matter  is  made  up  of  small  particles, 
and  that  these  small  particles  do  not  completely  fill  the  space 
occupied  by  the  body. 

Molecule  defined.  A  drop  of  water  is  made  up  of  count- 
less myriads  of  exceedingly  minute  particles.  If  you  will  in 
imagination  divide  and  subdivide  a  drop  of  water,  you  must 

WEED   CHEMISTRY 4 


52  CHEMISTRY   IN   THE   HOME 

at  last  have  a  particle  so  small  that,  if  you  divide  it  again, 
you  will  no  longer  have  water,  but  oxygen  and  hydrogen, 
the  elements  of  which  water  is  made.  This  smallest  particle 
of  water  that  can  exist  as  water  is  called  a  molecule.  We  may 
define  a  molecule  as  the  smallest  particle  of  any  substance, 
that  can  exist  in  the  free  state  and  still  be  that  substance.  Wood, 
sugar,  salt,  iron,  all  seemingly  so  solid,  are  in  reality  made  up 
of  molecules. 

Molecules  are  so  small  that  it  is  impossible  to  see  them, 
even  with  the  aid  of  the  most  powerful  microscope.  Small 
as  these  molecules  are,  it  is  .possible  to  obtain  by  physical 
methods  some  idea  of  their  size.  Lord  Kelvin  has  calculated 
that  the  distance  between  centers  of  contiguous  molecules  in  a 

solid .  must  be  not  more    than  -        inch,    and   may 

250,000,000 

be  only  one  half  of  this  distance.  If  then  you  will  cube 
250,000,000,  you  will  obtain  a  number  that  gives  the  smallest 
possible  number  of  molecules  in  a  cubic  inch.  The  number  is 
so  huge  that  we  are  totally  unable  to  obtain  any  real  idea  of 
its  value.  If  you  counted  one  molecule  each  second,  worked 
ten  hours  a  day,  and  300  days  a  year,  it  would  take  you  more 
than  23  years  to  count  one  line  of  molecules  one  inch  long. 

If  you  will  imagine  a  drop  of  water,  magnified  until  it  is  as 
large  as  the  earth,  the  water  molecules  would  be  somewhat 
smaller  than  baseballs.  It  is  difficult  for  us  to  imagine  the 
existence  of  these  molecules,  yet  it  is  only  by  believing  in 
their  existence  that  we  can  explain  many  of  the  laws  of 
chemistry  and  physics. 

Atoms  defined.  You  have  already  learned  that  certain 
substances,  as  oxygen,  gold,  and  iron,  are  called  elements 
because  we  have  found  it  impossible  to  pull  them  apart  and 
produce  from  them  other  and  simpler  substances.  You 


ATOMIC    THEORY  53 

have  also  seen  that  by  combining  elements  it  is  possible  to 
produce  new  substances,  as  when  you  combined  oxygen  and 
hydrogen  to  produce  water.  We  can  prove  that  one  mole- 
cule of  oxygen  will  combine  with  two  molecules  of  hydrogen 
to  form  two  molecules  of  water.  Since  each  molecule  of  the 
water  produced  contains  oxygen,  we  must  have  split  the 
oxygen  molecule  into  two  parts.  The  oxygen  molecule  must 
then  be  made  up  of  two  still  smaller  bodies,  and  to  these  we 
give  the  name  of  atoms.  We  may  then  define  an  atom  as  the 
smallest  part  of  the  molecule  of  an  element  that  can  combine  with 
other  atoms  to  form  molecules. 

The  difference  between  the  molecule  of  an  element  and  the 
molecule  of  a  compound  is  that  the  atoms  in  the  molecule 
of  the  element  are  all 


(o)  =  (o)  IH  -  (o)  ~  H) 

alike,  while  the  atoms    ^-^     ^^ 

in    the  molecule    of    a  FIG.  17.  —  1.  A  molecule  of  oxygen. 

compound  are  differ-  2'  A  molecule  of  watcr' 

ent.  The  molecule  of  oxygen  contains  two  small  bodies, 
exactly  alike,  called  atoms  of  oxygen,  held  together  by  a 
force  that  we  call  chemical  attraction  (Fig.  17).  The 
molecule  of  water,  on  the  other  hand  contains  two  like 
atoms  of  hydrogen  and  one  of  oxygen,  different  from  the 
other  two,  all  three  atoms  being  held  together  by  this  force 
of  chemical  attraction. 

Atoms  of  an  element  are  all  alike.  The  Law  of  Definite 
Proportions  proves  to  us  that  all  atoms  of  the  same  element 
are  alike.  If  every  atom  of  oxygen  did  not  have  exactly  the 
same  weight  as  every  other  atom  of  oxygen,  then,  in  water,  a 
compound  containing  oxygen  atoms,  the  proportion  by 
weight  in  which  the  oxygen  occurs  would  sometimes  vary. 
The  same  thing  is  true  of  atoms  of  all  other  elements.  If 
we  could  divide  a  particle  of  any  element  minutely  enough,  we 


54  CHEMISTRY   IN   THE  HOME 

would  obtain  molecules  first  and  then  atoms.  These  atoms 
would  all  be  exactly  alike.  Most  of  the  common  gaseous 
elements,  as  oxygen,  hydrogen,  and  nitrogen,  contain  two 
atoms  to  the  molecule. 

Law  of  Multiple  Proportions  explained.  How  can  we  ex- 
plain the  Law  of  Multiple  Proportions  ?  Since  the  amounts 
of  the  second  element  present  always  form  a  simple  ratio,  we 
have  evidently  one,  two,  or  three  atoms  of  the  second  element 
present.  That  is,  in  the  case  of  water,  we  have  two  atoms  of 
hydrogen  combining  with  one  atom  of  oxygen.  In  the  case 
of  hydrogen  peroxide,  we  have  two  atoms  of  hydrogen  unit- 
ing with  two  atoms  of  oxygen.  The  weights  of  oxygen  in 
the  two  compounds  must  be  as  one  is  to  two,  because  the 
number  of  atoms  is  as  one  is  to  two. 

Composition  of  molecules.  Molecules  of  elements  are 
composed  of  atoms,  and  these  are  all  alike.  Molecules  of 
compounds  are  composed  of  atoms,  and  these  atoms  are 
different.  Molecules  of  most  elements  contain  two  atoms, 
while  molecules  of  compounds  may  contain  from  two  to 
many  hundred  atoms.  The  molecule  of  albumen,  the  white 
of  egg,  contains  over  250  atoms,  while  the  number  of  atoms 
in  a  molecule  of  protoplasm  is  still  greater.  By  ways  that 
we  cannot  here  discuss,  chemists  have  determined  the  com- 
parative weights  of  these  tiny  atoms,  and  can  tell  how  many 
of  them  are  present  in  a  compound. 

Symbols  of  atoms.  Now  that  you  know  that  matter  is 
composed  of  atoms  and  molecules,  you  will  be  able  to  under- 
stand the  way  in  which  chemists  write  abbreviations  of  the 
names  of  these  atoms  and  molecules.  One  molecule  of  sugar 
is  composed  of  12  atoms  of  carbon,  22  atoms  of  hydrogen,  and 
11  atoms  of  oxygen.  To  write  all  this,  every  time  we  wish  to 
give  the  composition  of  a  sugar  molecule,  would  take  too 


ATOMIC   THEORY  55 

much  time.  Chemists  have  therefore  agreed  on  a  kind  of 
shorthand,  which  is  used  by  all  chemists,  no  matter  what 
their  nationality.  You  may  not  be  able  to  read  German, 
but  nevertheless  you  can,  if  you  understand  the  simple 
principles  used,  read  and  understand  the  abbreviations  in  a 
German  chemistry. 

The  symbol  of  one  atom  of  any  element  is  the  first  letter 
of  its  name,  written  as  a  capital.  Thus,  O  means  one  atom 
of  oxygen,  C  one  atom  of  carbon.  Where  there  are  several 
elements,  the  names  of  which  commence  with  the  same  letter, 
this  system  has  to  be  somewhat  modified.  In  these  cases 
we  use  two  letters,  writing  the  first  with  a  capital  and  the 
second  with  a  small  letter.  For  instance,  one  atom  of  carbon 
is  C,  one  atom  of  chlorine  Cl,  and  one  atom  of  chromium  Cr. 
Co  is  one  atom  of  cobalt,  but  CO  is  one  atom  of  carbon  and 
one  atom  of  oxygen. 

In  the  case  of  some  elements  that  have  been  known  for  a 
long  time,  we  use  in  their  abbreviations,  or  symbols,  the 
Latin  names.  Thus,  the  symbol  of  one  atom  of  sodium  is 
Na,  the  abbreviation  coming  from  the  Latin  name,  natrium. 
Some  others  are :  iron,  Fe,  from  ferrum ;  copper,  Cu,  from 
cuprum ;  mercury,  Hg,  from  hydrargeum.  A  complete  list 
of  symbols  is  given  in  the  table  of  physical  constants  of 
common  elements  in  the  appendix  (p.  378). 

Formulas  of  molecules.  Two  atoms  of  hydrogen  com- 
bine to  form  one  molecule.  We  must  have  some  way  of 
writing  the  symbol  of  hydrogen  so  as  to  distinguish  between 
two  separate  atoms  of  hydrogen  and  two  atoms  united  to 
form  one  molecule.  This  we  do  by  writing  a  figure  before 
or  after  the  symbol.  H  means  one  atom  of  hydrogen.  It  is 
not  necessary  to  write  the  coefficient  1 ;  it  is  understood.  To 
indicate  2,  3,  or  more  atoms  of  hydrogen,  we  write  a  co- 


56  CHEMISTRY   IN   THE   HOME 

efficient  in  front  of  the  symbol.  Thus,  when  we  wish  to 
indicate  two  atoms  of  hydrogen,  we  write  2H;  for  three 
atoms,  3  H. 

When  we  wish  to  indicate  that  two  atoms  of  hydrogen  are 
combined  to  form  a  molecule,  we  write  H2.  The  symbol 
H3  would  be  meaningless,  as  there  are  only  two  atoms  in 
one  molecule  of  hydrogen,  and  the  symbol  H3  would  mean  a 
molecule  made  up  of  three  atoms,  which  does  not  exist. 

The  formulas  of  molecules  of  compounds  are  written  in  the 
same  way.  A  molecule  of  water  is  composed  of  two  atoms  of 
hydrogen,  combined  with  one  atom  of  oxygen.  We  might 
write  the  formula  2  H  1  O,  but  this  would  be  inconvenient, 
as  when  we  wish*  to  write  two  molecules,  we  might  confuse 
the  coefficient  2  that  meant  two  molecules  with  the  coefficient 
2  that  meant  two  atoms  of  hydrogen.  We,  therefore,  in 
molecules  of  compounds,  write  the  number  that  expresses  the 
number  of  atoms  of  each  element  present  after,  instead  of 
before,  the  symbols  of  the  element.  We  also  write  it  below 
the  line.  The  formula  of  water  is,  then,  H2Oi;  but  since  it 
is  unnecessary  to  write  the  1,  the  formula  is  H2O. 

The  formula  of  sugar  is  C^H^On.  This  means  that  each 
molecule  of  sugar  is  made  up  of  12  atoms  of  carbon,  22  atoms 
of  hydrogen,  and  11  atoms  of  oxygen.  You  will  notice  that 
the  rule  that  there  are  two  atoms  of  hydrogen  in  a  molecule 
applies  only  to  the  element.  In  molecules  of  compounds 
there  may  be  any  number  of  hydrogen  atoms  present. 

Physical  and  chemical  change  defined.  Now  that  we 
know  what  matter  is  composed  of,  we  can  improve  our  defini- 
tions of  physical  and  chemical  changes.  A  physical  change 
is  one  in  which  no  new  molecules  are  formed,  but  where  the 
molecules  are  rearranged  or  separated.  A  chemical  change 
is  one  in  which  new  molecules  are  formed. 


ATOMIC   THEORY  57 

SUMMARY 

Small  units  of  matter.  All  matter  is  composed  of  atoms  and  mole- 
cules. 

A  molecule  is  the  smallest  particle  of  a  substance  that  can  exist  and 
have  the  properties  of  the  substance. 

An  atom  is  the  smallest  part  of  an  element  that  can  combine  with 
other  atoms  to  form  molecules. 

Law  of  Definite  Proportions.  The  composition  of  every  pure  chemi- 
cal compound  is  always  the  same. 

Law  of  Multiple  Proportions.  If  two  elements,  A  and  B,  combine  to 
form  more  than  one  compound,  the  weights  of  the  element  B 
that  combine  with  a  fixed  weight  of  the  element  A,  bear  a 
simple  ratio  to  each  other. 

Exercises 

1.  Is  there  any  difference  between  2H20,  and  H402?     Explain. 

2.  Is  there  any  difference  in  meaning  between  2H  and  H2? 
Explain. 

3.  What  difference  would  it  make  in  the  atomic  theory,  if  we 
should  find  that  lead  was  made  up  of  two  substances,  X  and  Y, 
instead  of  being  an  element  ? 

4.  Name  H,  H2,  2  H,  2  H2. 

6.   Does  H3  have  any  meaning? 

6.  How  many  atoms  are  there  in:  CuS04,  KC103,  C02,  HN03? 

7.  How  many  atoms  are  there  in  a  molecule  of  cane  sugar, 
C12H22Oii;  vinegar,  HC2H302;  washing  soda,  Na2C03  •  10  H20? 


CHAPTER  VII 
COMBUSTION 

Combustion  defined.  In  your  work  with  oxygen  you 
studied  the  burning  of  substances  such  as  charcoal,  sulphur, 
and  phosphorus,  and  reached  the  conclusion  that  burning 
was  a  combination  of  the  substance  burned  with  oxygen. 
Chemists  call  "  burning  "  combustion,  and  define  it  as  any 
chemical  change  accompanied  by  light  and  heat.  Oxygen 
is  the  great  supporter  of  combustion,  and  the  majority  of 
cases  of  combustion  that  you  will  encounter  are  combinations 
of  fuel,  such  as  coal  and  wood,  with  oxygen. 

Slow  oxidation.  The  ordinary  burning  of  wood  is  an 
oxidation  accompanied  by  light  and  heat,  called  by  chemists 
a  combustion.  Wood  can,  however,  combine  with  oxygen  so 
slowly  that  there  is  no  evidence  to  our  senses  of  either  light 
or  heat. 

If  you  have  ever  wandered  through  a  woodland,  you  must 
have  wondered  what  becomes  of  the  fallen  trees.  The 
ground  is  littered  with  fragments  of  bark  and  pieces  of 
rotten  wood,  but  despite  the  fact  that  trees  have  been  grow- 
ing in  that  ground  for  centuries,  there  is  no  large  accumulation 
of  wood  from  dead  trees.  We  should  expect  to  find  huge 
piles  of  wood  as  a  result  of  the  death  and  overthrow  of  the 
trees,  and  the  falling  of  twigs  and  boughs.  But  this  dead 
wood  has  combined  with  the  oxygen  of  the  air.  It  has  under- 
gone a  kind  of  burning.  The  same  products,  largely  carbon 

58 


COMBUSTION  59 

dioxide  and  water,  have  been  formed  as  if  the  wood  had  been 
burned  in  a  stove.  This  oxidation,  though,  has  been  so  slow 
that  at  no  one  time  has  heat  enough  been  generated  to  raise 
the  wood  to  a  temperature  at  which  it  would  give  a  large 
enough  amount  of  heat  to  be  perceptible  to  you.  Such  a 
slow  combination  with  oxygen  as  this  is  called  slow  oxidation. 
Some  chemists  call  it  slow  combustion.  The  final  products 
are  practically  the  same  as  in  quick  combustion,  and  the  total 
amount  of  heat  given  off  is  the  same,  but  the  heat  evolved 
is  distributed  over  such  a  long  time  that  the  substance  is 
not  appreciably  heated. 

Kindling  temperature  defined.  No  substance  will  burn 
until  it  has  been  heated  to  a  definite  temperature  called  its 
kindling  temperature.  This  temperature  varies  widely  for 
different  substances,  but  is  always  the  same,  for  the  same 
substance,  under  the  same  conditions.  You  have  used  one 
substance,  phosphorus,  which  has  a  low  kindling  tem- 
perature. Iron,  on  the  other  hand,  has  a  high  kindling 
temperature,  so  high  in  fact  that  most  people  do  not  realize 
that  it  can  be  burned. 

The  way  we  build  our  fires  well  illustrates  the  use  we  make 
of  various  kindling  temperatures.  We  first  place  paper, 
then  wrood,  and  lastly  coal  in  the  stove.  Then  we  strike  a 
match.  Friction  heats  the  composition  on  the  head  of  the 
match  to  its  kindling  temperature,  which  is  low,  and  the 
head  burns.  This  heats  the  wood  of  the  match  to  the  tem- 
perature at  which  it  ignites,  and  the  match  burns.  We 
then  touch  the  flame  of  the  match  to  the  paper  in  the  stove. 
The  paper,  because  its  kindling  temperature  is  fairly  low, 
and  because  we  need  heat  only  a  small  amount  of  it,  is 
easily  raised  to  the  required  temperature  and  bursts  into 
flame.  The  burning  paper  heats  the  wood  to  its  kindling 


60  CHEMISTRY   IN   THE   HOME 

temperature,  and  this  in  turn  heats  the  coal  until  it 
burns. 

Kerosene  burns  freely,  yet  a  lighted  match  can  be  thrust 
into  a  barrel  of  kerosene  without  danger.  The  match  does 
not  give  enough  heat  to  warm  the  kerosene  to  the  tempera- 
ture at  which  it  takes  fire.  If,  however,  you  should  throw  a 
cupful  of  kerosene  on  a  blazing  fire,  it  would  burn  fiercely. 
A  large  amount  of  coal  placed  on  a  feebly  burning  fire  extin- 
guishes it.  There  is  not  enough  heat  in  the  fire  to  warm  the 
coal  to  its  kindling  temperature,  and  so  the  fire  goes  out. 
Had  the  coal  been  added  gradually,  each  small  portion  would 
have  been  heated  to  its  kindling  temperature,  would  have 
caught  fire,  and  the  fire  could  have  been  saved. 

Spontaneous  combustion.  There  is  one  kind  of  combus- 
tion that  is  very  dangerous.  It  is  called  spontaneous  com- 
bustion. We  know  that  when  paint  is  first  put  on  a  house  it 
is  soft,  but  that  in  a  few  days  it  becomes  hard.  Paint  is 
composed  of  linseed  oil,  mixed  with  some  pigment,  and  the 
hardening  of  the  paint  is  due  to  the,  oxidation  of  the  oil, 
forming  a  solid  substance.  Many  oils  oxidize  in  the  same 
way.  As  in  every  case  of  oxidation,  heat  is  evolved.  In  the 
case  of  the  paint  on  the  house  this  heat  passes  into  the  air 
and  does  no  harm.  Suppose,  however,  you  wipe  up  the 
kitchen  floor  with  an  oily  rag,  and  then  place  the  rag  in  a 
pasteboard  box  in  a  closet.  The  oil  will  begin  to  oxidize. 
This  causes  heat,  and,  as  the  heat  cannot  easily  escape,  the 
rag  becomes  warm.  This  in  turn  hastens  the  oxidation, 
more  heat  is  evolyed,  and  soon  the  rag  is  in  flames. 

Damp  hay  tightly  packed  in  a  barn,  so  that  the  air  cannot 
circulate  through  it,  will  do  the  same  thing.  Even  soft 
coal  (bituminous  coal)  when  it  is  in  a  fine  powder  will  oxidize 
fast  enough  to  catch  fire,  and  ships  have  been  lost  at  sea 


COMBUSTION         ,  61 

because  of  their  cargo  of  coal  catching  fire  from  this  cause. 
The  remedy  in  the  home  is  never  to  put  away  oily  rags  where 
the  heat  produced  will  be  confined. 

Some  almost  unbelievable  things  have  happened  as  a 
result  of  unexpected  oxidation.  A  manufacturer  of  small  elec- 
tric motors  was  in  the  habit  of  allowing  the  steel  turnings 
he  produced  to  accumulate  until  there  were  enough  for  a  car 
load,  when  they  were  shipped  to  be  remelted.  One  winter  day, 
the  watchman  built  a  fire  near  the  heap.  The  heat  started 
the  steel  to  burning,  and  for  a  whole  day  in  spite  of  the 
streams  of  water  that  were  played  upon  it,  the  heap  of  steel 
burned.  Such  things  show  that  we  cannot  be  too  careful. 

What  to  do  in  case  of  fire.  The  danger  of  being  caught  in 
a  burning  building  is  one  to  which  we  are  all  exposed,  and, 
since  in  such  an  emergency  most  persons  lose  their  self-pos- 
session, it  will  be  well  for  you  to  think  in  advance  what  is 
the  best  course  to  pursue  in  such  a  case. 

If  awakened  in  the  night  by  the  smell  of  smoke,  do  not 
wait  to  dress  completely,  but  wrap  a  blanket  around  you, 
and  go  out  at  once.  Often  the  smoke  is  so  thick  that  it  is 
difficult  to  breathe.  The  air  close  to  the  floor  will  be  found 
purer  than  that  higher  up,  so  you  can  usually  get  through  a 
smoke-filled  hall  by  crawling  on  your  hands  and  knees.  A 
wet  cloth  held  to  the  nose  and  mouth  is  an  aid,  as  it  prevents 
the  inhalation  of  the  hot  air  and  smoke. 

Should  your  clothing  catch  fire  at  any  time,  do  not  run. 
This  only  serves  to  fan  the  flames.  Instead,  throw  yourself 
on  the  floor  and  slowly  roll  over  so  as  to  smother  the  flames. 
Often  a  blazing  skirt  can  be  torn  off,  or  the  fire  smothered 
by  throwing  a  rug  or  coat  over  it.  Above  all,  keep  calm. 
If  you  do,  you  will  escape  with  only  a  slight  injury,  while 
if  you  lose  your  head,  you  may  lose  your  life. 


62 


CHEMISTRY   IN   THE    HOME 


Should  a  small  fire  start  in  your  home,  it  can  usually  be 
extinguished  by  throwing  water  on  the  burning  substance, 
not  on  the  blaze.  A  bucket  kept  filled  with  water,  and  placed 
on  the  kitchen  shelf,  would  often  prevent  a  disastrous  loss. 
It  should  have  a  small  dipper  kept  in  it,  as  it  is  better  to 

throw  the  water  on  the 
fire  in  small  quantities, 
rather  than  to  pour  the 
contents  of  the  bucket 
on  the  fire  at  once.  A 
siphon  of  vichy  "makes 
a  very  good  fire  extin- 
guisher (Fig.  18).  It  is, 
however,  useless  to 
throw  a  small  quantity 
of  water  on  blazing  oil 
or  fat.  Such  fires  should 
be  smothered  with  sand, 
ashes,  or  flour,  or  a  wet 
cloth  or  rug. 

If  it  is  evident  that 
the  fire  is  beyond  con- 
trol, notify  the  fire  de- 
partment. You  should  know  the  position  of  the  fire-box 
nearest  your  home,  so  that  this  notice  can  be  quickly  given. 
If  you  have  a  telephone  in  the  house,  use  that.  Here, 
again,  the  number  of  the  fire  house  should  be  looked 
up  in  advance,  and  written  on  a  card  posted  near  the  tele- 
phone. It  is  easy  to  do  such  things  in  advance,  but  most  of 
us  neglect  them,  with  the  consequence  sometimes  that  our 
house  burns  down,  when  a  little  forethought  would  have 
saved  it.  Be  careful  to  close  the  door  when  you  leave  the 


FIG.   18.  —  Extinguishing  a  fire  with 
carbonated  water. 


COMBUSTION  63 

burning  room  to  give  the  alarm.  This  tends  to  confine  the 
fire  to  its  starting  point. 

The  average  fire  loss  in  the  United  States  is  over 
8200,000,000  annually.  Much  of  this  .comes  from  careless- 
ness in  the  use  of  matches.  Never  light  a  match  in  a  dark 
closet  filled  with  hanging  clothes.  Never  leave  matches 
where  small  children  can  play  with  them.  Never  keep 
matches  in  anything  but  metal  boxes.  Parlor  matches 
are  a  source  of  danger,  as  mice  gnaw  the  heads  and  thus 
cause  fires.  A  match  dropped  on  the  floor  may  be  stepped 
on,  and  so  cause  a  conflagration.  Safety  matches  cost 
but  little  more  than  parlor  matches,  and  are  much  safer. 

Methods  of  extinguishing  fire.  There  are  two  general 
methods  of  extinguishing  fires.  We  may  lower  the  tempera- 
ture of  the  burning  substance  below  its  kindling  temperature, 
or  we  may  smother  the  fire  by  shutting  off  the  supply  of 
oxygen. 

Carbon  tetrachloride,  CC14,  a  volatile,  non-combustible 
liquid,  is  a  good  fire  extinguisher.  A  little  thrown  on  a  fire 
gives  such  a  heavy  vapor  that  air  is  excluded  and  the  fire 
goes  out. 

Fireproofing  fabrics.  Conditions  often  arise,  as  in  theaters, 
where  light,  combustible  fabrics  must  be  exposed  to  the 
danger  of  contact  with  flame.  In  such  cases,  it  is  desirable 
to  fireproof  the  material.  This  may  be  done  by  the  use  of 
certain  salts,  as  ammonium  phosphate.  Either  of  the  fol- 
lowing formulas  may  be  used  to  fireproof  cotton  fabrics,  by 
soaking  them  in  the  liquid,  and  then  drying.  A  material 
treated  with  either  of  these  will  char,  but  will  not  burst 
into  flame.  The  cotton  bags  in  which  flashlights  are  set 
off  are  treated  with  a  similar  solution.  The  fireproofing 
should  be  repeated  every  time  the  article  is  laundered. 


64  CHEMISTRY   IN   THE    HOME 

(1)  Carbonate  of  ammonium 5    ounces 

Common  alum 10    ounces 

Boracic  acid 3    ounces 

Borax      . 3|  ounces 

Water 6    pints 

(2)  Ammonium  phosphate 8    ounces 

Boracic  acid 1    ounce 

Water 4J  pints 

A  similar  preparation  is  used  on  the  wood  from  which 
safety  matches  are  made.  Wood,  once  ignited,  glows  for 
some  time  after  the  flame  has  been  extinguished,  and  this 
spark  is  a  source  of  danger.  By  impregnating  the  wood, 
this  glowing  is  prevented,  and  a  match  carelessly  thrown 
down  cannot  cause  a  fire. 

If  the  articles  are  to  be  starched,  the  preparation  below 
may  be  used.1  The  materials  should  be  well  mixed. 

Hyposulphite  of  soda  (granulated)    .     .  3    pounds 

Cornstarch         3    pounds 

Common  salt 3    pounds 

Borax  (powdered) 1|  pounds 

Talcum  powder 3    pounds 

The  starch  is  made  by  taking  four  tablespoonfuls  of  this 
mixture  and  stirring  it  into  three  pints  of  boiling  water. 
The  mixture  thickens,  resembling  ordinary  starch,  and  is 
then  ready  for  use,  either  hot  or  cold.  The  articles  to  be 
starched  should  be  dipped  into  it,  allowed  to  remain  for  one 
minute,  removed,  and  wrung  out.  It  is  best  not  to  remove 
too  much  of  the  mixture.  Dry  and  iron  as  usual.  It  is 
not  necessary  to  wax  the  iron,  as  it  will  not  stick  to  the 
1  This  formula  is  due  to  Mr.  A.  J.  Jarman. 


COMBUSTION  65 

cloth.  The  use  of  such  a  preparation  would  often  avoid 
deplorable  accidents. 

Common  fuels.  There  are  three  fuels,  coal,  kerosene,  and 
illuminating  gas,  that  we  use  so  commonly  that  it  will  be 
worth  our  while  to  study  them  at  this  time.  Coal,  as  you 
will  find  in  a  later  chapter,  is  the  product  of  the  partial 
decay  of  vegetable  matter.  There  are  two  principal  varieties, 
anthracite,  or  hard  coal,  and  bituminous,  or  soft  coal.  They 
both  consist  mainly  of  carbon,  but  soft  coal  contains  in  addi- 
tion a  considerable  proportion  of  volatile  matter.  In  the 
eastern  cities,  hard  coal  is  used  in  the  household,  but  else- 
where in  the  country  soft  coal  is  generally  used. 

When  either  variety  burns,  the  carbon  combines  with  the 
oxygen  of  the  air  to  form  carbon  dioxide,  CO2,  while  any 
hydrogen  present  combines  with  oxygen,  forming  water. 
If,  however,  coal  is  burned  using  an  amount  of  air  insufficient 
for  complete  combustion,  the  carbon  burns  only  halfway, 
and  forms,  instead  of  carbon  dioxide,  the  gas  carbon  mon- 
oxide, CO.  This  gas  is  a  poison,  as  it  combines  with  the 
red  coloring  matter  of  the  blood,  and  renders  the  blood  in- 
capable of  absorbing  oxygen. 

How  to  regulate  coal  fires.  Since  ordinary  burning  is 
combining  with  oxygen,  when  we  wish  to  burn  coal  in  a 
stove  or  furnace,  we  must  provide  for  a  free  access  of  air. 
In  an  ordinary  range  (Fig.  19)  the  air  is  drawn  up  through 
the  grate  bars,  passes  through  the  coal,  burning  it,  and  the 
waste  gases  formed  then  escape  through  the  chimney.  To 
control  the  fire,  dampers  are  provided.  These  partially 
close  the  passage  through  which  the  gases  escape,  and  so 
diminish  the  amount  of  oxygen  fed  to  the  fire.  Thus  the 
fire  burns  less  briskly.  Closing  the  doors  under  the  fire 
does  the  same  thing,  that  is,  diminishes  the  supply  of  oxygen. 


66 


CHEMISTRY   IN   THE   HOME 


If  the  fire  is  not  raked,  the  accumulation  of  ashes  prevents 
the  passage  of  the  air,  and  the  fire  goes  out.  The  ash  that 
forms  when  coal  is  burned  comes  from  the  mineral  matter  in 
the  vegetation  from  which  the  coal  was  formed. 

It  is  often  desirable  to  keep  the  fire  over  night  when  no 
heat  is  needed.     This  can  be  done  by  shutting  the  dampers, 


Damper 


FIG.  19.  —  Diagram  of  cooking  range. 

and  lightly  covering  the  fire  with  ashes.  The  fire  will  then 
smolder,  and  in  the  morning,  a  little  fresh  coal,  raking, 
and  opening  the  dampers  will  quickly  revive  it.  Examine 
the  stove  or  furnace  in  your  house,  and  see  if  you  can  find 
out  how  the  fire  is  controlled. 

Heating  value  of  coal.  Coal  varies  much  in  its  heating 
power.  One  pound  of  good  coal  should  be  able  to  heat 
14,000  pounds  of  water  1°  F.  Large  corporations  now  buy 


COMBUSTION 


67 


coal  on  the  basis  of  its  fuel  value,  instead  of  by  the  ton.  It 
would  not  pay  you  to  have  the  necessary  analysis  made  to 
enable  you  to  do  this,  so  you  will  have  to  trust  to  the  coal 
dealer.  One  thing  though  you  can  do,  and  that  is  to  watch 
the  amount  of  ash  that  forms.  Good  coal  should  not  give 
over  10%  of  ash  by  weight.  If  you  find  that  your  coal 
gives  more  than  this,  it  is  well  to  buy  another  brand  next 
time.  The  veins  of  coal  in  the  mine  occur  between  layers 
of  slate,  and  this  is  often  not  completely  removed  from 
the  coal.  You  should,  of  course,  not  buy  coal  that  on  exam- 
ination shows  slate  mixed  with  it. 

Kerosene.  Kerosene  is  a  mixture  of  a  number  of  com- 
pounds known  collectively  as  hydrocarbons.  They  are  all 
compounds  of  carbon  and  hydrogen,  and 
on  burning  form  carbon  dioxide  and 
water.  If  you  have  a  kerosene  lamp, 
notice  that,  when  it  is  first  lighted,  a 
mist  collects  on  the  inside  of  the  chimney. 
This  is  water  formed  by  the  burning 
hydrogen  of  the  kerosene  combining  with 
the  oxygen  of  the  air.  As  the  chimney 
becomes  hot,  the  water  evaporates.  By 
keeping  the  chimney  cold  by  surround- 
ing it  with  a  water  jacket,  the  water  will 
continue  to  be  deposited  until  at  last  it 
will  run  down  in  drops. 

From  what  you  have  learned  about 
combustion  you  will  see  the  advantage 
of  the  lamp  chimney  (Fig.  20).  If  we  are  to  burn  enough 
kerosene  to  give  a  bright  light,  we  must  have  a  plentiful 
supply  of  air.  The  chimney  gives  this  by  creating  a  good 
draft.  If  we  turn  the  lamp  too  high,  it  smokes.  Know- 

WEED   CHEMISTRY 5 


FIG.  20.  —  Lamp  show- 
ing air  currents. 


68  CHEMISTRY   IN   THE   HOME 

ing  the  eagerness  with  which  hydrogen  and  oxygen  com- 
bine, you  can  explain  this  smoking.  If  we  turn  the  wick 
too  high,  we  vaporize  so  much  kerosene  that  there  is  not 
enough  oxygen  in  the  air  in  the  chimney  to  burn  both  the 
hydrogen  and  the  carbon  of  the  kerosene.  Since  oxygen 
would  rather  combine  with  hydrogen  than  with  carbon, 
the  hydrogen  burns  and  leaves  the  carbon  free.  This  carbon 
is  the  smoke  that  is  sometimes  so  annoying,  and  blackens 
the  ceiling  over  a  lamp  or  a  gas  flame. 

When  we  wish  to  manufacture  lampblack,  advantage  is 
taken  of  this  fact.  We  burn  a  hydrogen  and  carbon  com- 
pound, as  natural  gas,  in  an  insufficient  amount  of  air.  The 
flame  smokes,  and,  on  collecting  the  smoke,  we  have  lamp- 
black. 

Luminous  flames  explained.  To  produce  a  flame,  we 
must  have  a  burning  gas.  In  the  case  of  the  lamp,  the  heat 
of  the  flame  converts  the  liquid  kerosene  into  a  gas.  This 
burns,  and  gives  the  flame.  You  will  remember  that  hydro- 
gen burns  with  a  flame,  but  that  this  flame  is  colorless.  Since 
the  only  difference  between  the  hydrogen  and  kerosene  flame 
is  the  presence  of  carbon,  the  color  of  the  flame  must  in  some 
way  be  due  to  the  carbon.  The  probable  explanation  is 
this.  The  heat  of  the  flame  decomposes  the  kerosene,  and 
sets  the  carbon  free  in  the  form  of  very  small  particles. 
Since  there  is  no  oxygen  in  the  interior  of  the  flame,  these 
carbon  particles  cannot  burn,  but  are  heated  and  glow  with  a 
yellow  light.  When  they  reach  the  edge  of  the  flame,  where 
they  encounter  the  oxygen  of  the  air,  they  burn,  and,  forming 
carbon  dioxide,  disappear.  This  explains  why  a  thin,  flat, 
wick  is  used.  It  gives  more  surface  for  oxygen  to  reach  the 
carbon  and  so  combustion  is  more  perfect. 

By  lowering  a  cold  plate  over  a  kerosene  or  a  luminous  gas 


COMBUSTION 


69 


flame  for  a  few  seconds,  you  will  find,  on  removing  it,  that 
carbon  is  deposited  on  the  plate  in  the  form  of  lampblack. 
This  is  because  the  cold  plate  cools  the  carbon  in  the  flame 
below  its  kindling  temperature,  so  that  it  cannot  burn. 

The  Bunsen  burner.  Illuminating  gas  is  a  mixture  of 
hydrogen,  carbon  monoxide,  and  some  gases  rich  in  carbon. 
The  hydrogen  and  carbon  monoxide  burn  and  furnish  heat, 
while  the  other  gases  set  free 
carbon  which,  being  heated, 
gives  a  luminous  flame.  The 
products  of  this  combustion 
are  of  course  the  same  as  in 
the  case  of  kerosene.  In  the 
gas  stove,  we  do  not  need  a 
luminous  flame,  but  we  do  re- 
quire a  hot  flame.  We  gain 
this  by  using  what  is  called  a 
Bunsen  burner  (Fig.  21).  The 
difference  between  this  and  an 
ordinary  burner  is  that,  in  the 
Bunsen  burner,  air  is  mixed 
with  the  gas  before  it  is  burned. 
Instead  of  the  hydrogen  and  carbon  having  to  pass  through 
the  flame,  and  come  to  the  edge  before  burning,  they  burn 
in  the  flame.  The  carbon  then  does  not  pass  in  an  incan- 
descent state  through  the  flame  and  so  the  flame  is  non- 
luminous.  The  Bunsen  burner  flame  is  much  hotter  than 
the  ordinary  luminous  flame. 

To  obtain  a  perfect  Bunsen  burner  flame  requires  a 
nice  adjustment  of  air  and  gas.  This  is  accomplished  by 
turning  the  regulator  that  opens  and  closes  the  air  holes  at 
the  base  of  the  burner,  until  the  flame  is  colorless,  but  does 


FIG.  21.  —  Section  of  a  Bunsen 
burner. 


70 


CHEMISTRY   IN   THE    HOME 


not  hiss.  When  using  a  gas  stove,  you  will  sometimes  find 
that  a  kettle  put  over  the  flame  becomes  covered  on  the 
bottom  with  a  coat  of  soot.  This  is  because  the  burner  is 
not  properly  adjusted.  You  can  remedy  the  trouble  easily, 
if  you  will  examine  the  construction  of  the  burner,  and  bear 
the  above  facts  in  mind. 

A  gas  and  air  mixture  is  an  explosive.  A  mixture  of  air 
and  illuminating  gas  forms  a  violent  explosive.  Therefore, 
do  not  carry  a  flame  into  a  room  containing  such  a  mixture. 
Many  bad  accidents  have  been  caused  by  persons  lighting  a 
match  to  look  for  a  bad  gas  leak.  Bear  this  in  mind  when 
you  light  the  gas  oven.  Some  cooks 
have  turned  on  the  gas,  and,  after 
allowing  it  to  mix  with  the  air  in  the 
oven,  have  lighted  it.  You  can  imagine 
the  consequences. 

Welsbach  gas  burners.  The  in- 
tensely hot  flame  of  theBunsen  burner, 
although  it  is  itself  non-luminous,  may 
be  used  to  produce  a  bright  light.  The 
oxides  of  certain  rare  metals,  when 
heated  to  a  high  temperature,  glow 
brightly.  By  immersing  a  loosely 
woven  cotton  wick  in  a  solution  of  the 
mixed  nitrates  of  these  metals,  drying 

it,  and  then  burning  the  cotton,  the  nitrates  decompose, 
forming  oxides,  which  are  left  in  the  shape  of  the  original 
wick.  The  result  would  be  too  delicate  to  transport.  It  is 
therefore  dipped  in  collodion.  This  forms  a  flexible  protec- 
tive coating  over  the  whole.  In  this  form  you  buy  it  as  the 
mantle  of  a  Welsbach  burner  (Fig.  22).  When  the  mantle 
is  placed  in  position  and  set  on  fire,  the  collodion  burns  off, 


FIG.  22.  —  Gas  mantle. 


COMBUSTION 


71 


leaving  the  oxides  behind  as  a  fragile  web.  This  is  heated 
by  the  hot,  non-luminous  Bunsen  burner  flame  of  the 
Welsbach  burner,  and  gives  an  intense  light. 

These  burners  use  only  a  small  quantity  of  gas,  and  are 
very  bright.  Their  disadvantage  is  the  delicate  mantle. 
A  slight  jar  is  sufficient  to  break  it  to  fragments.  The  in- 
verted form  of  mantle  is  especially  useful,  as  there  is  nothing 
under  the  light,  and  therefore  the  illumination  is  sent  with- 
out waste  where  it  is  most  useful. 

Reading  your  gas  meter.  Stores  are  continually  offering 
new  forms  of  gas  burners  and  gas  heaters,  and  the  statement 


FIG.  23.  —  Gas  meter  dial. 

is  usually  made  that  they  burn  such  a  small  amount  of  gas 
that  their  cost  is  saved  in  a  very  short  time.  Naturally,  the 
manufacturer  of  such  devices  is  inclined  to  underestimate  the 
gas  consumption,  and  it  is  well  for  you  to  be  able  to  find  out 
for  yourself  just  how  expensive  their  use  is.  This  you  can 
do  by  learning  to  read  the  gas  meter. 

When  you  study  this  lesson,  as  a  part  of  your  work,  exam- 
ine your  gas  meter.  You  will  find  a  series  of  dials  at  the 
top,  and  over  each  dial  a  figure  (Fig.  23).  The  arrange- 
ment is  not  alwavs  the  same,  but  usually  there  are  three 


72  CHEMISTRY   IN   THE   HOME 

dials,  marked  1  thousand,  10  thousand,  100  thousand.  Each 
dial  is  divided  into  ten  parts,  and  these  parts  are  numbered 
from  one  to  ten.  The  number  over  the  dial  means  the  num- 
ber of  cubic  feet  of  gas  that  one  revolution  of  the  pointer 
measures.  Thus,  when  the  1  thousand  dial  hand  has  made 
one  complete  revolution,  one  thousand  cubic  feet  of  gas  have 
passed  through  the  meter. 

The  exact  mechanical  arrangement  is  difficult  to  explain 
without  the  use  of  an  actual  meter,  but  the  principle  is  this. 
The  meter  contains  a  pair  of  bellows.  The  pressure  of  the 
gas  causes  the  gas  to  flow  into  one  of  these  bellows  and  fill  it. 
As  the  bellows  expands,  it  moves  a  wheel  that  is  connected 
to  the  dial  on  top,  and  thus  causes  the  pointer  to  go  around. 
These  pointers  are  so  connected  that  one  complete  revolu- 
tion of  the-1  thousand  hand  advances  the  10  thousand  hand 
one  tenth  of  a  revolution.  Thus  it  takes  ten  revolutions  of 
the  1  thousand  hand  to  make  the  10  thousand  hand  go  around 
once.  As  you  burn  the  gas,  it  slowly  flows  out  of  the  full 
bellows,  which  collapses,  while  at  the  same  time  the  empty 
bellows  fills. 

The  position  of  the  pointers  of  these  dials  is  read  by  the 
meter  inspector,  each  month,  and  by  subtracting  the  reading 
of  the  last  month  from  the  reading  of  this  month,  the  gas 
company  can  tell  how  many  thousand  cubic  feet  you  have 
used,  and  so  what  your  bill  will  be.  The  next  time  your 
meter  is  read,  go  with  the  inspector  and  read  it  also.  Tell 
him  what  your  reading  is,  and  ask  him  if  it  is  correct.  You 
will  then  be  sure  that  you  understand  just  how  the  amount 
of  gas  you  use  is  determined. 

At  the  extreme  top  of  the  meter  there  is  usually  a  small 
dial  that  registers  two  cubic  feet.  By  using  this  small  dial 
you  can  tell  just  how  much  gas  the  various  burners  of  your 


COMBUSTION  73 

gas  stove  or  gas  lights  use.  Be  sure  that  all  the  gas  jets  in  the 
house  are  closed.  Light  the  burner,  the  consumption  of 
which  you  wish  to  know.  Wait  until  the  pointer  on  the  small 
dial  is  exactly  over  a  mark,  and  then  note  the  exact  time, 
using  the  second  hand  of  a  watch.  When  the  hand  has  made 
one  complete  revolution,  note  the  time  again.  You  now 
know  how  many  minutes  that  particular  burner  takes  to 
burn  two  cubic  feet  of  gas.  A  simple  calculation  will  tell 
you  the  number  of  cubic  feet  burned  per  hour,  and,  knowing 
the  cost  of  a  thousand  cubic  feet,  you  can  compute  the  ex- 
pense per  hour.  In  this  way  you  can  compare  the  efficiency 
of  two  styles  of  burners,  or  compute  the  expense  of  heating 
a  room  by  the  use  of  a  small  gas  stove.  It  is  more  accurate 
if,  instead  of  using  only  one  revolution  of  the  small  hand,  you 
allow  the  burner  to  use  enough  gas  to  cause  the  hand  to 
make  two  or  three  revolutions. 

This  small  hand  may  also  be  used  to  test  for  the  pres- 
ence of  a  leak.  Note  the  exact  position  of  the  small  hand 
in  the  morning,  being  careful  to  see  that  all  the  gas  cocks 
in  the  house  are  turned  off.  Read  its  position  in  the 
evening,  before  any  gas  is  turned  on.  •  A  change  in  the 
position  of  the  hand  shows  the  presence  of  a  leak. 

Gas  flatiron.  One  simple,  useful  gas  device  is  the  gas- 
heated  flatiron.  In  the 
summer  a  small  kitchen 
becomes  uncomfortably 
hot,  if  the  flatirons  are 
heated  over  the  gas  stove 
on  ironing  day.  This 

excessive     heat     may     be  FIG.  24.  -  A  gas-heated  flatiron. 

avoided  by  using  a  gas  iron  (Fig.  24).  It  is  like  an  ordinary 
flatiron,  but  is  made  hollow  to  allow  the  use  of  a  Bunsen 


74  CHEMISTRY   IN   THE    HOME 

flame  on  the  inside.  This  heats  the  iron,  and  avoids  the 
necessity  of  changing  irons.  The  consumption  of  gas  is 
not  large.  If  you  have  one  at  home,  it  will  be  worth  while 
to  test  its  consumption  of  gas  and  find  out  just  what  it  costs 
to  operate  it.  Test  also  the  gas  consumption  of  the  burner 
that  you  would  use  to  heat  the  ordinary  iron,  and  you  can 
tell  whether  it  is  a  real  economy  to  use  a  gas-heated  flat  iron. 
How  to  use  a  gas  stove  economically.  Care  in  the  use  of 
gas  stoves  will  enable  you  to  save  a  considerable  proportion 
of  your  gas  bill.  In  using  a  gas  oven,  for  example,  it  is 
often  possible,  when  the  roast  is  almost  cooked,  to  turn  off 
the  gas  and  let  the  heat  of  the  oven  finish  the  cooking.  The 
use  of  a  fireless  cooker  will  still  further  cut  the  consumption 
of  gas.  You  will  find  this  described  in  another  chapter. 

SUMMARY 

Combustion  is  any  chemical  change  accompanied  by  light  and  heat. 

Oxidation  is  union  with  oxygen.  It  may  be  slow  or  rapid.  When 
it  is  rapid  enough,  it  becomes  combustion. 

Kindling  temperature  is  the  temperature  at  which  a  body  will  begin 
to  burn. 

Flame  is  burning  gas. 

Kerosene  forms  water  and  carbon  dioxide  when  it  burns. 

Luminous  flames  are  often  due  to  incandescent  carbon. 

A  Welsbach  burner  light  is  due  to  the  incandescent  mantle. 

Spontaneous  combustion  is  combustion  which  occurs  when  no  defi- 
nite outside  heat  has  been  furnished  to  raise  the  body  to  its 
kindling  temperature.  It  is  brought  about  by  slow  oxidation 
under  conditions  which  prevent  the  scattering  of  the  heat  so 
produced. 

Exercises 

1.  What  is  an  explosion  ? 

2.  Can  flour  dust  explode?     Explain. 

3.  Why  is  oily  waste  kept  in  metal  cans  in  shops  ? 


COMBUSTION  75 

4.  Can  hydrogen  be  used  in  a  Welsbach  burner?     Explain. 

5.  Why  is  gasoline  not  suitable  for  use  in  a  lamp? 

6.  What  would  be  the  result  of  throwing  a  lighted  match  into  a 
barrel  of  gasoline  ?     Of  sewing  machine  oil  ? 

7.  Why  is  water  a  poor  thing  to  use  to  extinguish  an  oil  fire? 
What  would  you  use  and  why? 

8.  Why  is  a  heap  of  fine  soft  coal  dust  dangerous? 

9.  Why  is  it  necessary  to  rake  the  ashes  from  under  the  fire? 

10.  What  does  it  mean,  when  your  Welsbach  mantle  becomes 
covered  with  a  black  deposit  ?     How  would  you  remedy  the  trouble  ? 

11.  What  should  you  do  with  a  rag  with  which  you  have  oiled 
the  furniture?     Why? 

12.  State  in  the  order  in  which  you  would  do  them,  all  of  the 
things  you  would  do,  if  a  fire  broke  out  in  your  house. 

13.  Where  does  the  fire  escape  on  your  house  lead  to? 

14.  Where  is  the  fire  alarm  box  nearest  to  your  house  ? 

15.  How  would  you  get  to  the  roof  of  your  house  ?     Can  you 
walk  from  the  roof  of  your  house  to  other  houses  ? 

16.  If  a  fire  should  start  in  your  house,  would  you  go  upstairs  or 
downstairs,  and  why? 

17.  What  steps  should  be  taken  to  prevent  an  explosion  in  a 
mine  full  of  fine  coal  dust  ? 

18.  Why  are  lace  curtains  and  a  gas  flame,  both  near  a  window, 
a  dangerous  combination? 


CHAPTER  VIII 
HEAT 

Work  defined.  In  the  study  of  heat  we  need  to  understand 
the  exact  physical  meaning  of  two  words,  work  and  energy. 
In  physics,  we  do  not  regard  everything  that  you  might  call 
labor  as  work.  If  you  should  support  a  pail  of  water  in  your 
hand,  without  motion,  you  would  not  be  doing  work  in  a 
mechanical  sense.  To  do  work  on  the  pail  of  water,  you 
must  lift  it.  By  work  we  mean  overcoming  some  resistance 
(as  lifting  a  weight)  through  some  distance.  The  element  of 
time  does  not  come  into  the  thought  at  all. 

A  convenient  unit  by  which  to  measure  work  is  the  foot 
pound.  If  you  lift  one  pound  one  foot,  against  the  force  of 
gravity,1  you  do  one  foot  pound  of  work.  It  makes  no 
difference  how  long  you  take  to  do  this,  the  amount  of  work 
done  remains  the  same.  If  you  lift  6  pounds  4  feet,  you  do 
6  X  4  =  24  foot  pounds  of  work.  You  can  measure  work, 
then,  by  multiplying  together  the  number  of  pounds  lifted 
by  the  vertical  distance  through  which  they  are  lifted.  It 
may  interest  you  to  calculate  the  foot  pounds  of  work  you 
do  in  going  from  the  street  to  the  top  floor  of  the  building. 

Energy  defined.  Energy  is  the  capacity  for  doing  work. 
When  you  walk  upstairs,  you  are  lifting  the  weight  of  your 
body,  or  you  are  expending  energy.  Winding  a  watch  gives 
energy  to  the  spring.  It  is  then  capable  of  doing  work  in 

1  We  call  the  force  that  tends  to  pull  bodies  to  the  earth  gravity. 

76 


HEAT 


77 


making  the  wheels  of  the  watch  rotate.  Coal  possesses 
energy,  for  in  burning,  it  may  cause  water  to  boil,  and  the 
steam  thus  produced  may  be  used  in  a  steam  engine,  which  in 
turn  may  be  used  to  lift  a  weight. 

Our  great  source  of  energy  is  the  sun.  The  energy  con- 
tained in  the  sunlight  causes  the  grass  to  grow.  A  cow  eats 
the  grass,  and  converts  it  into  beef.  You  eat  the  beef,  and 
convert  its  energy  into  the  energy  contained  in  the  muscle 
of  your  arm.  This  muscular  energy  you  use  in  winding  up 
tlie  spring  of  your  watch.  The  energy  thus  given  to  the 
spring  enables  it  to  cause  the  wheels  to  rotate.  This  rotation 
causes  heat,  which  passes  off  into  space.  In  this  series  of 
energy  transformations,  you  have  changed  its  form,  but  have 
neither  created  nor  destroyed 
energy.  This  fact,  that  we 
can  neither  create  nor  destroy 
energy,  is  called  the  Law  of  the 
Conservation  of  Energy. 

Heat  is  a  form  of  energy. 
For  many  years  heat  was 
thought  to  be  a  material 
substance  called  phlogiston. 
That  is,  a  body,  after  it  had 
been  burned,  was  believed  to 
weigh  less  than  before,  because 
the  phlogiston  had  been  taken 
from  it.  This  belief  we  now 
know  was  incorrect,  for  bodies  gain  in  weight  when  they 
are  burned.  This  we  can  prove  by  weighing  all  of  the 
products  formed,  the  gases  as  well  as  the  solids. 

When  two  pieces  of  wood  are  rubbed  together,  they  become 
hot.     In  fact,  so  much  heat  is  thereby  developed  that  savages 


FIG.  25.  —  Primitive  method  of 
making  fire  by  friction. 


78  CHEMISTRY   IN   THE   HOME 

have  used  this  method  to  obtain  fire  (Fig.  25).  Since  the 
wood  does  not  change  in  weight,  mechanical  motion  (energy) 
must  have  been  converted  into  heat.  It  is  always  true  that  a 
body  in  motion  possesses  energy,  and  that  anything  that 
arrests  this  motion  converts  this  energy  into  heat.  This 
energy  change  may  be  reversed.  That  is,  heat  may  be  used 
to  cause  motion,  as  when  the  energy  contained  in  steam, 
due  to  its  heat,  is  used  to  run  a  steam  engine.  Such  facts  as 
these  cause  us  to  believe  that  heat  is  a  form  of  energy. 

When  we  heat  a  body,  the  particles  (molecules)  composing 
it  are  set  in  motion.  The  faster  the  molecules  vibrate,  the 
hotter  the  body  becomes.  The  energy  that  you  put  into  the 
body  is  changed  into  molecular  motion.  The  difference, 
then,  between  a  cold  and  a  hot  piece  of  iron  is  simply  that,  in 
the  hot  piece  the  particles  of  iron  composing  it  are  moving 
more  rapidly  than  are  those  in  the  cold  piece.  These  iron 
particles,  called  molecules,  are  so  small  that  we  cannot  see 
them,  yet  their  velocity  can  be  measured. 

Fahrenheit  and  Centigrade  thermometers.  Calorie  de- 
fined. You  must  carefully  distinguish  between  degree  of 
heat  and  amount  of  heat.  Boiling  water  under  standard 
(barometer  reading  30  inches)  conditions  always  has  the 
same  temperature,  212°  F.  A  pint  of  boiling  water,  however, 
cannot  contain  as  much  heat  as  a  quart  of  boiling  water, 
although  its  temperature  is  the  same.  We  measure  degrees 
of  heat  by  the  aid  of  a  thermometer.  To  measure  quantity 
of  heat,  you  must  learn  a  new  unit,  the  calorie.  A  calorie 
is  the  amount  of  heat  that  will  raise  the  temperature  of  one 
gram  of  water  1.8°  F.  (1°  C.). 

There  are  two  thermometer  scales  in  use, —  the  Fahrenheit 
and  the  Centigrade  scales  (Fig.  26).  The  Centigrade  scale 
divides  the  distance  between  the  freezing  and  boiling  points 


HEAT 


79 


CENTIGRADE 
100' 


-182.5- 


-273°  - 


of  Water 


FAHRENHEIT 
212° 


--Room  Temperature--- 

^Freezing  Point_ 
of  Water" 


of  water  into  100  degrees,  calling  the  freezing  point  of  water 
0°  C.,  and  the  boiling  point  100°  C.  On  the  Fahrenheit 
scale,  this  interval  is  divided  into  212-32  or  180  degrees. 
Thus,  100  Centigrade  degrees  corresponds  to  180  Fahrenheit 
degrees,  or  1°C.=  1.8°  F.  The 
real  definition  of  the  calorie  is, 
the  amount  of  heat  that  will 
raise  the  temperature  of  one 
gram  of  water  one  degree  Cen- 
tigrade. Since  we  use  the 
Fahrenheit  scale  in  our  work, 
we  put  instead  of  1°  C.,  its 
equivalent,  1.8°  F.  The  large 
calorie,  or  Calorie,  is  equiva- 
lent to  1000  calories.  In  our 
study  of  foods  we  shall  use 
Calories  constantly. 

Absolute  zero  defined.  Since 
the  temperature  of  a  body 
depends  on  the  rate  at  which 
its  molecules  are  vibrating, 
when  a  body  is  cooled,  this 
molecular  motion  must  become 
less.  Evidently  there  must 
come  a  time  when  the  mole- 
cules are  at  rest,  and  at  this 
temperature  there  must  be  an 
absolute  absence  of  heat.  This 
temperature  is  called  the  abso- 
lute zero.  On  the  Fahrenheit  s 
Centigrade  scale  it  is  —  273°. 


Boiling  Point  of 
Oxygen 


— Absolute  Zero — 


-296.5 


-459.4 


FIG.  26.  —  Comparison  of  Centi- 
grade and  Fahrenheit  scale. 

scale  it  is  -  459.4°,  on  the 


Heating  a  body  consists  in 
causing  its  molecules  to  move  more  rapidly.     This  differ- 


80  CHEMISTRY   IN   THE   HOME 

ence  in  the  rate  at  which  the  molecules  are  moving  is  the 
only  difference  between  a  cold  and  a  hot  body.  The  hot- 
test thing  that  we  can  make  is  the  electric  arc,  which  may 
reach  a  temperature  of  about  6000°  F.  The  temperature  of 
the  sun  is  much  higher  than  this. 

Solids,  liquids,  and  gases  defined.  It  is  the  amount  of 
motion  of  the  molecules  that  determines  the  physical  state 
of  a  substance,  that  is,  whether  it  is  a  solid,  a  liquid,  or  a 
gas.  In  solids  the  molecules  vibrate  more  or  less  rapidly, 
but  do  not  change  their  relative  positions  in  the  body.  The 
molecules  attract  each  other.  In  liquids,  the  molecules  not 
only  vibrate  back  and  forth,  but  are  able  to  change  their 
positions  relative  to  each  other.  There  is,  however,  a  feeble 
attraction  between  the  molecules.  In  gases  there  is  not 
only  no  attraction  between  the  molecules,  but  they  repel 
each  other,  trying  to  separate  as  widely  as  possible. 

These  facts  will  enable  you  to  understand  why  the  following 
definitions  are  true.  A  solid  is  a  substance  that  does  not 
take  the  shape  of  the  vessel  in  which  it  is  placed.  Solids  have 
a  definite  weight,  volume,  and  shape.  A  liquid  is  a  substance 
that  takes  the  shape  of  the  vessel  in  which  it  is  placed. 
Liquids  have  a  definite  weight,  a  definite  volume,  but  no 
definite  shape.  A  gas  is  a  substance  that  takes  the  shape 
of  any  vessel  in  which  it  is  placed,  and  distributes  itself 
uniformly  throughout  the  space.  Gases  have  a  definite 
weight,  but  neither  a  definite  volume  nor  shape. 

Sources  of  heat.  The  great  source  of  heat  in  nature  is  the 
sun.  If  it  should  fail  us,  the  earth  would  soon  become  a 
dead  planet.  Fortunately,  there  is  no  reason  to  anticipate 
any  such  calamity.  Other  sources  of  heat  are  the  ulterior 
heat  of  the  earth,  heat  caused  by  friction,  and  heat  due  to 
chemical  action.  In  this  last  we  are  especially  interested. 


HEAT  81 

Effects  of  heat.  When  we  heat  or  cool  a  body,  that  is, 
when  we  add  to  or  subtract  from  its  energy,  a  number  of 
effects  may  be  produced.  The  temperature  of  the  body  may 
change,  or  it  may  change  its  physical  state,  that  is,  a  solid 
•may  melt,  or  a  liquid  be  converted  into  a  gas.  Also  the  pres- 
sure of  the  body  upon  the  containing  vessel  may  change,  as 
in  gases,  or  its  properties,  as  hardness,  color,  electrical  con- 
ductivity, and  volume,  may  vary. 

Heat  expands  bodies.  When  a  body  is  heated,  it  expands. 
This  is  true  of  solids,  liquids,  and  gases,  with  practically  no 
exceptions.  The  way  in  which  water  expands  is  somewhat 
unusual,  and  it  will  be  well  for  you  to  refer  back  to  the  chap- 
ter on  water  and  review  the  facts.  The  expansion  of  solids 
may  cause  the  housekeeper  expense  and  annoyance.  If,  in 
washing  a  large  cut  glass  bowl,  you  put  it  at  once  into  hot 
water,  it  is  apt  to  crack.  This  is  due  to  unequal  expansion, 
caused  by  the  outside  of  the  bowl  becoming  hot,  while  the 
inside  is  still  cool.  The  remedy  is  to  put  the  bowl  first  into 
lukewarm  water,  and  then  to  raise  the  temperature  slowly 
by  pouring  in  hot  water.  The  same  principle  applies  when- 
ever breakable  objects  are  to  be  heated.  Suddenly  cooling 
a  hot  glass  will  also  crack  it.  Why  ? 

The  raising  of  cake  is  partly  due  to  the  expansion  of  a 
gas.  When  the  batter  is  placed  in  the  oven,  the  innumerable 
gas  bubbles,  derived  from  the  reaction  between  the  com- 
pounds of  the  baking  powder  distributed  through  it,  are 
heated,  the  gas  expands,  and  so  the  cake  is  made  light. 
Why,  then,  do  you  think  that  banging  the  oven  door,  soon 
after  the  cake  has  been  put  in,  is  likely  to  make  the  cake  fall  ? 
Those  of  you  who  have  made  popovers  know  how  essential 
it  is  that  the  batter  be  very  thin.  If  it  is  too  thick,  the  force 
of  the  expanding  gas  is  not  sufficient  to  lift  the  upper  crust, 


82  CHEMISTRY   IN   THE    HOME 

and  a  tough  doughy  mass  results,  instead  of  a  light  puffy 
one. 

Heating  bodies  changes  their  physical  state.  Another 
effect  of  heat  is  change  of  state.  If  you  leave  an  open  pan 
of  water  exposed  to  the  air,  the  water  slowly  disappears. 
It  evaporates.  This  process  will  go  on  until  either  the  pan 
is  empty,  or  until  the  air  has  become  saturated  with  water 
vapor.  If  you  heat  the  water,  you  will  find  that  the  change 
from  a  liquid  to  a  vapor  proceeds  more  rapidly.  When  you 
have  heated  the  water  to  212°  F.,  it  boils.  That  is,  bubbles 
of  steam  form  all  through  the  mass  of  the  water. 

This  change  of  liquid  to  a  vapor  is  called  vaporization  or 
volatilization.  When  the  change  occurs  at  low  temperatures, 
the  liquid  is  said  to  be  volatile.  Alcohol  and  gasoline  are 
volatile  liquids.  Most  solids  when  heated,  first  liquefy 
(melt),  and  then  vaporize.  A  few,  as  sal  ammoniac  (ammo- 
nium chloride),  iodine,  and  camphor,  pass  directly  from  the 
solid  to  the  gaseous  state  and  when  this  vapor  is  cooled,  it 
returns  to  the  solid  state  without  passing  through  the  liquid 
state.  This  we  call  sublimation.  The  substance  is  said  to 
sublime,  and  the  solid  product  obtained  is  called  a  sublimate. 

Water  will  evaporate,  even  when  it  is  in  the  form  of  ice. 
Wet  clothes,  hung  out  in  the  winter  to  dry,  first  freeze,  and 
then  dry  by  evaporation  of  the  ice. 

Fractional  distillation.  The  rate  of  evaporation  depends 
upon  many  things.  First,  upon  the  boiling  point  of  the 
liquid.  The  nearer  a  liquid  is  to  its  boiling  point,  the  faster 
it  evaporates.  Water  boils  at  212°  F.,  while  alcohol  boils 
at  173°  F.  If,  then,  we  heat  both  alcohol  and  water  to 
160°  F.,  the  alcohol  will  evaporate  the  faster,  because  it  is 
nearer  to  its  boiling  point.  Advantage  is  taken  of  this  fact 
in  fractional  distillation.  If  we  heat  a  mixture  of  alcohol 


HEAT  83 

and  water,  the  alcohol  will  distill  off  first,  leaving  the  water 
behind.  The  alcohol  will  not  be  quite  anhydrous  (water 
free),  but  nearly  so.  This  process  is  often  used  to  separate 
two  liquids  having  different  boiling  points. 

Conditions  affecting  evaporation.  The  rate  of  evaporation 
also  depends  on  the  extent  of  surface  exposed.  The  larger 
the  surface,  the  more  freely  the  air  will  dissolve  the  liquid. 
Liquids  to  be  evaporated  should  be  placed  in  large  shallow 
pans,  rather  than  in  deep  narrow  vessels.  When  the  air 
over  the  liquid  becomes  saturated  with  its  vapor,  evaporation 
ceases.  Evaporation  in  a  deep  vessel  is  very  slow  because 
the  air  is  renewed  with  difficulty  and  quickly  becomes 
saturated  with  the  vapor.  In  chemical  works,  a  blast  of 
air  is  sometimes  blown  across  the  evaporating  liquid,  so  as 
to  bring  dry  air  continually  in  contact  with  it.  Would  you 
expect  clothes  to  dry  faster  on  a  windy  or  on  a  still  day? 
Why?  Do  clothes  dry  faster  on  a  cool  or  a  warm  day? 
Why  ?  In  the  sun  or  the  shade  ?  Why  ?  The  drying  of 
clothes  is  of  much  importance  to  the  housekeeper. 

Amount  of  water  evaporated  from  the  earth's  surface. 
The  total  amount  of  water  evaporated  from  the  earth  each 
year  is  enormous.  The  average  yearly  rainfall  is  between 
30  and  40  inches.  All  this  water  (about  175  pounds  for 
each  square  foot  of  the  earth's  surface)  must  first  be  evapo- 
rated by  the  air  before  it  can  fall  as  rain.  The  largest  amount 
of  this  water  comes  from  the  ocean,  but  plants  furnish  more 
than  is  generally  realized.  In  hot  weather,  grass  loses  by 
evaporation,  each  day,  its  own  weight  of  water,  or  about  6J 
tons  per  acre.  Trees  also  contribute  much  water  vapor  to 
the  air. 

Boiling  explained.  If  the  temperature  of  a  liquid  is  contin- 
uously raised,  we  at  last  reach  a  temperature  at  which  the 

WEED    CHEMISTRY 6 


84 


CHEMISTRY   IN   THE   HOME 


liquid  boils.  Bubbles  of  gas  are  then  formed  all  through  the 
mass  of  the  liquid,  and  these  gas  bubbles  in  escaping  set  the 
mass  of  the  liquid  into  violent  agitation.  The  temperature 
then  remains  unchanged  until  the  liquid  has  all  boiled  away. 
The  explanation  of  boiling  is,  that,  as  the  temperature  of 
the  liquid  is  raised,  its  molecules  are  set  into  more  and  more 
violent  motion.  This  motion  increases  until  those  molecules 
that  are  on  the  surface  of  the  liquid  are  thrown  so  far  into 
the  air  that  they  escape  from  the  attraction  of  the  liquid. 
We  say  that  water  boils  at  212°  F.  This  is  not  always  true. 
From  the  explanation  of  boiling  given  above,  you  will  see 
that  the  rapid  escape  of  the  molecules  from  the  surface  of  a 
liquid  must  depend  upon  the  pressure  on  that  surface.  If 
the  pressure  is  diminished,  the  number  of  molecules  present 

above  the  liquid  is  lessened,  and 
it  is  then  easier  for  new  molecules 
to  escape,  or,  in  other  words,  the 
boiling  point  is  lowered.  If  the 
pressure  is  increased,  the  reverse 
change  takes  place,  or  the  boiling 
point  is  raised.  This  may  be 
shown  by  half  filling  a  round- 
bottomed  flask  with  water,  and 
boiling  the  water  until  the  steam 
formed  has  driven  all  of  the  air 
from  the  flask.  The  flame  is  then 
removed,  and  the  flask  corked.  If  cold  water  is  now  poured 
on  the  flask,  some  of  the  steam  is  condensed  (Fig.  27) .  This 
lowers  the  pressure,  and  the  water  inside  the  flask  boils 
furiously.  This  may  be  continued  until  the  water  in  the  flask 
is  so  cool  that  you  may  place  your  hand  on  the  flask,  and  yet 
the  water  inside  is  boiling. 


FIG.  27.  —  Boiling  water  at 
reduced  pressure. 


HEAT  85 

Advantage  of  boiling  under  diminished  pressure.  Many 
liquids  cannot  be  boiled  at  ordinary  pressures  and  tempera- 
tures without  a  chemical  change  taking  place.  When  it  is 
necessary  to  evaporate  such  liquids,  we  place  them  in  a 
closed  vessel,  and  pump  off  the  air  and  vapor  from  above 
them.  In  this  way  the  pressure  on  the  liquid  is  diminished, 
the  boiling  point  of  the  liquid  lowered,  and  evaporation, 
without  decomposition,  becomes  possible.  This  is  always 
done  in  sugar  refineries  in  evaporating  sugar  solutions. 

Effect  of  altitude  on  the  boiling  point.  As  we  climb  moun- 
tains the  air  pressure  becomes  less.  At  the  top  of  Mount 
Blanc,  the  pressure  is  so  low  that  water  boils  at  183°  F.  In 
Denver,  at  an  altitude  of  something  over  5000  feet,  water 
boils  at  203°  F.  This  makes  a  serious  difference  to  a  cook. 
The  temperature  of  boiling  water  in  Denver  is  so  much  lower 
than  it  is  with  us,  that  it  is  necessary  to  boil  meat  and  vege- 
tables there  much  longer  than  in  New  York.  This  dimin- 
ished pressure  does  not  of  course  affect  the  time  required  to 
roast  meat,  as,  in  roasting,  the  meat  is  exposed  to  the  direct 
heat  of  the  fire. 

Effect  of  dissolved  substances  on  the  boiling  point.  The 
boiling  point  also  depends  upon  the  purity  of  the  liquid. 
The  effect  of  any  dissolved  solid  is  to  raise  the  boiling  point. 
Thus,  water  saturated  with  calcium  chloride  does  not  boil 
until  a  temperature  of  354°  F.  has  been  reached.  The 
presence  of  dissolved  solids  also  lowers  the  freezing  point  of 
liquids.  Sea  water,  for  example,  does  not  freeze  at  32°  F., 
but  at  a  lower  temperature. 

Transferring  heat  by  conduction.  There  are  three  ways 
in  which  heat  is  conveyed  from  place  to  place,  conduction, 
convection,  and  radiation.  A  common  case  of  the  transfer 
of  heat  by  conduction  is  in  the  use  of  a  flatiron.  The  cold 


86 


CHEMISTRY   IN   THE    HOME 


iron  when  placed  on  the  stove  is  first  heated  on  the  bottom. 
The  heating  sets  the  bottom  particles  of  the  iron  into  rapid 
vibration,  they  strike  against  their  neighbors,  setting  these 
in  motion,  and  this  continues  until  every  particle  of  the  iron 
is  rapidly  moving,  or,  until  the  entire  mass  of  iron  is  hot. 


FIG.  28.  —  Circulation  of  air  in  a  refrigerator. 

Iron  is  said  to  be  a  good  conductor  of  heat,  because  heat 
easily  travels  through  it  in  this  way. 

Wood,  on  the  other  hand,  is  a  poor  conductor  of  heat. 
There  is  no  difficulty  in  holding  a  lighted  match,  because 
heat  travels  so  slowly  through  the  mass  of  the  wood,  that, 
although  one  end  of  the  match  is  burning,  the  other  end  is 
cold.  Cloth  is  also  a  poor  conductor  of  heat.  It  is  for  this 
reason  that  you  use  a  cloth  pad  in  handling  a  hot  flatiron, 


HEAT 


87 


as  heat  does  not  pass  readily  through  the  cloth.  Metals, 
on  the  other  hand,  are  good  conductors  of  heat,  silver  being 
the  best.  You  may  have  noticed  how  quickly  a  silver  spoon, 
placed  in  hot  coffee,  becomes  hot. 

Air  is  one  of  the  poorest  conductors  of  heat.  Woolen  dress 
goods  are  warm  for  this  reason.  The  wool  fibers  entangle 
large  amounts  of  air  among  them,  and  it  is  this  entrapped  air 
that  makes  a  woolen  sweater  warm.  Linen,  on  the  other  hand, 
does  not  do  this,  and  so  linen  is  cool. 

You  may  sometime  when  going  skating  have  wrapped  a 
newspaper  around  your  body  to  keep  you  warm.  It  is  really 
the  air  confined  bet\veen  the  layers  of  paper  that  is  the  non- 
conductor, and  so  prevents  the  heat  of  the  body  from  escap- 
ing. Do  you  think  that  a  thick  piece  of  cardboard  would 
give  you  better  protection? 

A  refrigerator  is  of  necessity  built  of  non-conducting 
materials  (Fig.  28).  An  iron  refrigerator  would  be  useless, 
as  heat  would  be  so  quickly  conducted  through  it  that  ice 
in  the  interior  of  it  would  not  keep  for  any  length  of  time. 
In  practice  refriger- 
ators are  built  of  I  lf«  R  ol 

Q  I .1  |__          j__    |_  £  u>          \^)  ^  _j 

wood,  with  an  inside  H    <*^      §    u  ||2  &£ 

lining  of  porcelain 
or  metal.  The  space 
between  these  two 
walls  is  filled  with 
various  non-con- 
ducting materials 
(Fig.  29). 

Comparative  conductivity  of  different  materials.  We  can 
easily  measure  the  comparative  thermal  conductivity  of 
different  substances.  Roughly,  if  we  represent  the  con- 


FIG.  29. 


Section  through  the  wall  of  a 
refrigerator. 


CHEMISTRY   IN   THE    HOME 


ductivity  of  silver  by  10,  the  .conductivity  of  copper  is  8.5, 
iron  2,  wood  0.003,  and  flannel  0.0004.  These  numbers  are 
only  approximations,  but  will  serve  to  show  the  great  differ- 
ences that  exist  in  the  conductivity  of  different  materials. 

It  will  be  an  interesting  home  experiment  for  you  to  select 
two  similarly  shaped  saucepans,  one  of  enamel  and  one  of 
steel,  pour  a  glass  of  water  in  each,  place  them  on  the  stove, 
and  "see  in  which  case  the  water  boils  first.  You  will  learn 
something  about  the  conducting  power  of  enamel  that  will 
be  of  use  to  you. 

Convection.  Heat  is  transmitted  through  air  by  a  process 
called  convection.  The  air  over  a  hot  surface  is  heated  (Fig. 

30),  this  air  expands, 
and,  becoming  of  a 
less  specific  gravity,1 
rises.  Its  place  is 
taken  by  cooler  air, 
and  the  process  is 
repeated.  By  this 
means  the  air  in 
the  schoolroom  is 
warmed. 

Since  the  warm  air 
is  continuously  ris- 
ing, the  temperature  is  highest  in  the  upper  part  of  the  room. 
Mothers  sometimes  forget  this  fact,  and  fancy,  that,  because 

1  By  specific  gravity  we  mean  the  weight  of  a  substance,  compared 
to  the  weight  of  the  same  volume  of  some  other  substance  that  is 
used  as  a  standard.  For  solids  and  liquids,  th:s  standard  is  water, 
for  gases  the  standard  is  hydrogen.  The  specific  gravity  of  sul- 
phuric acid  is  1.84,  that  is,  any  given  volume  of  sulphuric  acid  (as  one 
quart)  will  weigh  1.84  times  as  much  as  the  same  volume  (one  quart) 
of  water. 


FIG.  30.  —  Circulation  of  air  in  room  warmed 
by  a  radiator. 


HEAT  89 

the  air  is  warm  where  they  are  sitting,  it  will  also  be  warm 
enough  for  the  baby  playing  on  the  floor.  This  is  by  no 
means  always  the  case,  and  often  the  child  suffers  from  cold, 
when  the  upper  layers  of  the  air  in  the  room  are  warm  enough. 

Heat  is  transmitted  in  gases  almost  exclusively  by  con- 
vection. The  same  is  largely  true  in  liquids.  Water  is  an 
extremely  poor  conductor  of  heat.  If  you  will  fill  a  test  tube 
with  water  and,  holding  it  by  the  bottom,  place  the  top  in  a 
flame,  you  will  find  that  you  can  boil  the  water  in  the  upper 
part  of  the  tube,  while  the  water  in  the  bottom  of  the  tube 
is  not  even  warmed. 

The  explanation  of  convection  in  liquids  is  the  same  as  in 
the  case  of  gases.  The  liquid  in  contact  with  the  hot  surface 
is  heated,  expands,  becomes  of  less  specific  gravity,  rises, 
and  is  replaced  by  the  cooler  liquid. 

Radiation.  Radiation  is  the  third  means  of  transfer  of 
heat,  and  requires  a  little  more  detailed  explanation.  There 
is  no  air  or  any  other  form  of  ordinary  matter  between  the 
earth  and  sun.  It  is  therefore  impossible  that  the  heat  of 
the  sun  should  reach  the  earth  by  the  processes  of  conduction 
or  convection.  We  must  imagine  a  totally  different  method 
of  transmission. 

We  believe  that  all  space  is  filled  with  an  extremely  rarefied 
substance  that  is  called  the  luminiferous  ether,  or,  more 
simply,  the  ether.  (This  is  not  the  liquid  used  by  surgeons 
to  produce  insensibility,  but  a  totally  different  substance.) 
This  ether  is  not  like  ordinary  matter,  but  has  some  very 
wonderful  properties.  It  is  impossible  to  pump  it  out  of 
any  vessel.  For,  supposing  it  were  possible  to  draw  it  out 
from  the  top,  it  would  leak  in  through  the  sides,  between 
the  molecules  of  which  the  vessel  was  composed.  Nor  is  it 
possible  to  pump  more  ether  into  a  bottle  than  it  already 


90  CHEMISTRY   IN   THE   HOME 

contains,  for  an  attempt  to  do  so  would  simply  force  ether 
out  through  the  sides  of  the  bottle.  So  far  as  we  know,  this 
ether  can  penetrate  any  body. 

If  we  could  magnify  a  drop  of  water  sufficiently,  it  would 
somewhat  resemble  lemon  jelly,  filled,  not  too  closely,  with 
caraway  seeds.  The  lemon  jelly  would  represent  the  ether, 
and  the  caraway  seeds  the  particles  (molecules)  of  the  water. 
Suppose  now  that  you  had  a  room  filled  with  such  a  jelly, 
and  should  strike  the  jelly  on  one  corner.  A  quiver  would 
run  through  the  entire  mass  of  the  jelly,  just  as  it  does  in  a 
mold  of  ordinary  jelly  on  the  table.  This  quiver  may  be 
called  a  wave.  You  know  that  when  a  wave  moves  through 
the  water,  the  wave  moves  onward,  but  the  water  particles 
simply  rise  and  fall  as  is  shown  by  a  piece  of  wood  floating 
on  the  waves.  So,  in  the  case  of  the  jelly,  the  wave  moves 
through  it,  but  the  motion  of  any  part  of  the  jelly  is  only 
back  and  forth. 

Imagine  now  the  ether  stretching  from  the  sun  to  the  earth. 
Some  very  hot  particle  at  the  surface  of  the  sun,  by  reason  of 
its  high  temperature,  is  in  violent  motion,  and  therefore  has 
energy.  This  moving  particle  strikes  the  ether  a  blow  and 
so  causes  in  it  a  wave  motion.  This  wave  runs  through  the 
mass  of  the  ether  until  finally  it  strikes  the  earth.  There, 
the  wave  strikes  some  material,  perhaps  a  stone.  The 
energy  of  the  wave  is  used  up  in  setting  the  molecules  of  the 
stone  in  motion,  that  is,  in  heating  it.  That  a  wave  can  in 
this  way  transmit  energy  is  shown  by  the  destructive  action 
of  water  waves  in  wearing  away  the  shore. 

You  must  understand  that,  while  the  wave  is  passing  from 
the  sun  to  the  earth,  it  is  not  heat,  but  only  a  wave  in  the  ether. 
It  is  not  until  this  wave  strikes  some  material  object,  that  its 
energy  is  changed  into  heat. 


HEAT 


91 


The  velocity  of  these  ether  waves  is  very  great,  about 
186,000  miles  per  second.  They  can  transmit  not  only  heat 
energy,  but  light  and  electrical  energy  as  well.  It  is  by  the 
use  of  ether  waves  that  wireless  telegraphy  is  possible.  The 
difference  between  the  ether  waves  that  produce  heat  and 
those  that  produce  light  is  in  their  wave  length,  that  is, 
the  distance  from  the  top  of  one  wave  to  the  top  of  the  next. 
Heat  waves  are  longer  than  light  waves. 

You  can  now  understand  why  a  glass  greenhouse  is  so  much 
warmer  than  the  outside  air,  even  though  it  is  not  heated 
artificially.  Ether  waves  coming  from  the  sun  can  pass 
freely  through  the  glass.  These  waves  strike  the  plants 
and  soil  and  are  converted  into  heat.  Glass  is  a  poor  con- 
ductor of  heat,  and  so  the  heat  cannot  pass  through  the  glass 
by  conduction.  The  air  in  the  greenhouse  is  confined,  so 
that  heat  cannot  escape  by  convection.  The  air  in  the 
greenhouse  is  therefore  heated.  The  process  of  heat  transfer 
by  ether  waves  is  A 

called  radiation,  and 
the  energy  of  such 
ether  waves  is  called 
radiant  energy. 

Laws  of  radiant 
energy.    Radiant  en-  M 

erffV  obeVS  the  same  ^1 

'  &J  y 

laws,  whether  we  are 
dealing  with  light  waves  or  heat  waves.  These  waves  are 
absorbed  by  dull,  and  reflected  from  polished,  surfaces. 
They  travel  in  straight  lines.  When  they  are  reflected  from 
polished  surfaces  the  angle  of  incidence  equals  the  angle  of 
reflection,  as  is  shown  in  Fig.  31. 
These  laws  explain  many  facts  that  you  are  familiar  with. 


N 


>  —  MN  is  the  reflecting  surface.     ^  BOA 
(incidence)  =ZAOC  (reflection). 


92 


CHEMISTRY   IN   THE   HOME 


A  white  dress  is  cooler  than  a  black  one  because  radiant  heat 
is  reflected  better  from  white  than  from  black.  Milk  keeps 
better  in  a  polished  can  than  in  a  dull  one  for  the  same  reason. 
The  bottom  of  your  teakettle  should  not  be  polished,  be- 
cause you  want  the  heat  to  be  absorbed  and  not  reflected. 
It  should  not,  however,  be  thickly  covered  with  soot,  for 
that  is  a  poor  conductor  of  heat.  A  screen  placed  in  front 
of  a  fire  protects  you  from  the  heat,  because  it  reflects  the 
ether  waves.  Many  similar  examples  of  the  application  of 
these  laws  to  life  will  occur  to  you,  if  you  will  try  to  think  of 
them. 

Fireless  cookers.  The  fireless  cooker  now  so  widely 
advertised  is  a  practical  application  of  a  number  of  principles 

of  heat.  In  boiling 
meat,  for  example,  it 
is  necessary  to  keep 
the  meat  for  some 
time  at  about  the 
temperature  of  boil- 
ing water.  This  can 
be  done  by  heating 
it  on  the  stove  to  the 
boiling  point,  and 
then  placing  the  pot 
in  some  vessel  pro- 
vided with  a  non-conducting  outside  layer,  such  as  a  fireless 
cooker  (Fig.  32). 

A  simple  but  efficient  fireless  cooker  can  be  made  at  home. 
Fill  a  box  with  some  non-conducting  material  as  hay  or  saw- 
dust. Leave  a  hole  in  the  center  in  which  to  place  the  pot, 
and  provide  a  cover,  which  also  has  a  layer  of  cloth  stuffed 
with  hay  over  it.  Such  a  simple  device  will  keep  a  liquid 


FIG.  32.  —  Fireless  cooker. 


HEAT 


93 


hot  for  many  hours.  It  may  also  be  used  as  a  refrigerator, 
for  the  non-conducting  material  will  not  only  keep  heat  in, 
but  will  also  keep  heat  out.  Doubtless  you  can  now  tell 
why  a  woolen  dress  will  keep  you  warm,  and  yet  a  piece  of 
woolen  cloth  wrapped  around  a  piece  of  ice  will  keep  it  from 
melting. 

The  manufacture  of  artificial  ice.     When  a  gas  is  liquefied 
heat  is  given  off,  and  when  the  liquid  changes  back  to  a  gas 


EXPANS/ON  CYL/MOEft. 


u 

HI  \ 

BRINE.    1C  £  CAN. 

FIG.   33.  —  Manufacture  of  artificial  ice  by  the  ammonia  process. 

it  absorbs  heat.  This  principle  is  extensively  utilized  in  the 
manufacture  of  artificial  ice.  Ammonia  gas  is  cooled  and 
compressed  until  it  changes  to  a  liquid.  As  a  result  of  this 
compression,  the  liquid  would  become  very  hot,  but  it  is 
cooled  by  keeping  it  surrounded  by  cool  running  water. 
This  liquid  ammonia  is  then  run  into  a  coil  of  large  pipe, 
where  it  boils,  changing  back  into  a  gas.  The  boiling  point 
of  liquid  ammonia  is  very  low,  but  it  takes  heat  to  change 
it  into  a  gas  just  the  same.  This  heat  must  come  from  the 


94  CHEMISTRY   IN   THE   HOME 

coil  of  pipe  in  which  the  ammonia  is  placed,  so  the  pipe  be- 
comes very  cold.  This  coil  of  pipe  in  turn  is  surrounded  by 
a  strong  brine,  and  the  cold  pipe  cools  the  brine.  You  have 
learned  that  dissolving  solids  in  water  lowers  its  freezing 
point,  so,  although  the  brine  is  cooled  to  about  16°  F.,  it 
does  not  freeze.  Cans  containing  pure  water  are  suspended 
in  the  brine.  This  pure  water  is  then  cooled  by  the  brine  to 
32°  F.,  when  it  freezes.  The  ammonia  gas  that  is  formed  is 
pumped  out  of  the  pipes,  once  more  compressed  to  a  liquid, 
and  used  over  again. 

Ice  prepared  in  this  way  is  purer  than  natural  ice,  and 
preferable  for  domestic  use.  One  pound  of  it  will  do  the  same 
work  in  cooling  that  a  pound  of  natural  ice  will ;  there  is  no 
difference,  as  both  have  the  same  temperature,  32°  F. 
Ammonia  is  not  the  only  substance  that  can  be  used  in  prepar- 
ing artificial  ice,  but  it  has  the  advantages  of  cheapness 
and  safety. 

SUMMARY 

Work  is  the  overcoming  of  resistance  through  distance. 

Energy  is  the  capacity  for  doing  work. 

Law  of  Conservation  of  Energy :    Energy  can  neither  be  created  nor 

destroyed. 

Heat  is  a  form  of  energy. 

Solids  have  a  definite  weight,  a  definite  volume,  and  a  definite  shape. 
Liquids  have  a  definite  weight,  a  definite  volume,  and  no  definite 

shape. 
Gases  have  a  definite  weight,  no  definite  volume,  and  no  definite 

shape. 
A  calorie  is  the  amount  of  heat  needed  to  warm  one  gram  of  water 

one  degree  Centigrade.     A  Calorie  equals  1000  calories. 
On  the  Centigrade  scale  water  boils  at  100°  and  freezes  at  0°. 
On  the  Fahrenheit  scale  water  boils  at  212°  and  freezes  at  32°. 
Conversion  of  one  scale  reading  to  the  other.    To  convert  F.°  to  C.° : 
(F.°  -  32)  ^  1.8  =  C.° 


HEAT  95 

To  convert  C.°  to  F.° : 

(C.°  X  1.8)  +  32  =  F.° 

Conduction  is  the  transfer  of  heat  from  particle  to  particle. 
Convection  is  the  transfer  of  heat  due  to  the  mechanical  motion  of 

heated  particles. 
Radiation  is  the  transfer  of  heat  by  radiant  energy,  or  waves  in  the 

ether. 

Exercises 

1.  Why  is  a  fur  coat  so  warm? 

2.  Should  ice  be  placed  in  the  top  or  bottom  of  a  refrigerator? 
Explain. 

3.  Draw  a  diagram  of  a  refrigerator  showing  the  air  currents 
inside. 

4.  We  use  electric  fans  in  summer  to  cool  ourselves,  yet  in  winter 
an  electric  fan  directed  toward  a  radiator  will  cause  a  cool  room  to 
become  warm  quickly.     Explain. 

5.  What  is  the  principle  of  a  Thermos  bottle  ? 

6.  Glue  is  prepared  from  bones  by  heating  them  in  water  to  a 
temperature  of  more  than  212°  F.     How  is  this  possible? 

7.  Water  boils  at  214°  F.,  at  the  level  of  the  Dead  Sea.     How 
can  this  be  ? 

8.  In  warm  climates,  water  is  cooled  by  placing  it  in  a  porous 
jar  (similar  to  a  flower  pot),  and  hanging  the  jar  in  the  shade,  but 
where  the  wind  will  strike  it.     Explain. 

9.  The  temperature  of  islands  is  more  equable  than  that  of  con- 
tinents.    This  is  due  to  the  water  surrounding  them.     Explain. 

10.  Dew  seldom  falls  on  a  windy  night.     Why? 

11.  Why  do  double  windows  keep  a  room  warm? 

12.  Should  hot-air  radiators  be  placed  at  the  top  or  bottom  of  a 
room?     Why? 

13.  Draw  a  diagram  showing  how  your  house  is  heated. 

14.  Why  do  not  apples  freeze  when  the  temperature  drops  to 
just  32°  F.? 

15.  Covering  the  ice  in  a  refrigerator  with  a  piece  of  carpet  will 
cause  the  ice  to  melt  very  slowly.     Is  it  well  to  do  this  ? 

16.  How  can  food  be  cooked  in  a  fireless  cooker  ?     Explain. 

17.  Why  are  water  pipes  buried  deeply  in  the  ground? 


CHAPTER   IX 
THE  ATMOSPHERE 

Air  is  matter.  That  we  live  at  the  bottom  of  an  ocean  of 
an  invisible  gas,  the  air,  is  a  fact  that  we  quite  generally 
ignore.  It  is  only  when  this  gas  is  set  in  violent  motion,  as 
in  hurricanes,  tornadoes,  and  cyclones,  that  we  take  notice 
of  it,  and  yet  our  very  existence  depends  upon  its  presence, 
for  without  oxygen,  one  of  the  gases  found  in  it,  we  could 
not  live. 

We  have  found  that  steam  is  an  invisible  gas  made  by 
boiling  water.  If  we  could  not  cool  steam  and  so  change  it 
to  water,  we  would  find  it  hard  to  believe  that  it  was  really 
composed  of  ordinary  matter.  Air,  too,  is  such  an  invisible 
gas,  and  consists  of  ordinary  matter.  This  is  shown  by  the 
fact  that  it  may  be  changed  to  a  liquid  by  cooling  and  com- 
pression. 

Since  the  boiling  point  of  liquid  air  is  below  any  tempera- 
ture that  naturally  exists  upon  the  earth  (  —  312°  F.),  air 
never  exists  in  nature  in  the  form  of  a  liquid.  When  liquid 
air  is  cooled  to  a  still  lower  temperature,  it  is  changed  to  a 
transparent  solid  similar  to  ice. 

That  a  so-called  empty  bottle  is  not  really  empty  is  easily 
shown  (Fig.  34).  If  we  tightly  fit  a  cork,  through  which 
we  have  thrust  a  funnel,  into  the  mouth  of  an  empty  bottle, 
and  then  pour  water  into  the  funnel,  only  a  little  water  will 
run  through  the  funnel  into  the  bottle.  The  reason  for  this 

96 


THE    ATMOSPHERE 


97 


is  that  the  bottle  is  filled  with  this  invisible  gas  that  we  call 
air,  and  two  bodies  cannot  occupy  the  same  space  at  the 
same  time.  At  first,  a  little  water  runs  into  the  bottle.  The 
air  is  compressed,  since  the  cork  prevents  its  escape,  but  soon 
the  pressure  of  the  water  trying  to  get  in  is  balanced  by  the 
pressure  of  the  air  trying  to  get  out,  and  so  no  more  water 
can  enter.  We  can,  however,  by  the  aid  of  a  second  tube 


Water  Pressure 


passed  through  the  cork,  let  the 
air  out,  in  which  case  the  water 
quickly  runs  in  and  fills  the  bottle. 

Air,  then,  in  spite  of  the  fact 
that  we  do  not  usually  recognize 
its  existence,  occupies  space,  and 
is  real  matter.  That  air  has 
weight  can  be  shown  by  weighing 
a  glass  bulb  fitted  with  a  stop- 
cock, and  then  pumping  the  air 
out  of  the  bulb  and  weighing  it 
again.  The  difference  in  the  two 
weights  must  represent  the  weight 
of  the  volume  of  air  in  the  bulb. 
If  this  volume  is  measured,  the 
weight  of  a  known  volume  of  air 
can  be  determined.  In  this  way 
the  weight  of  a  cubic  yard  of  air 
has  been  found  to  be  2.18  pounds.  That  is,  roughly  speak- 
ing, 13  cubic  feet  of  air  weigh  a  pound. 

It  is  this  weight  of  the  air,  combined  with  its  high  velocity, 
that  makes  high  winds  so  destructive,  and  that  makes  air 
offer  such  a  high  resistance  to  rapidly  moving  objects. 

The  barometer.  The  fact  that  air  has  weight  can  be  shown 
in  another  way.  Fill  with  mercury  a  long  tube  one  square 


FIG.  34.  —  The  so-called  "empty 
bottle"  contains  air. 


98  CHEMISTRY   IN   THE   HOME 

inch  in  cross  section,  and  closed  at  one  end,  and  invert  it  in 
a  dish  of  mercury  (Fig.  35).  Since  the  end  of  the  tube  that 
dips  in  the  mercury  is  open,  you  might  expect  the  mercury 
in  the  tube  to  run  out,  and  it  does  do  so  until  the  height  of 
the  mercury  in  the  tube  is  about  30  inches. 
Then  it  remains  stationary. 

Since  the  mercury  stays  in  the  tube,  some- 
thing must  be  holding  it  there,  and  this  some- 
thing is  the  weight  of  the  air  pressing  on  the 
mercury  in  the  dish.  If  we  remove  this  pressure 
by  placing  the  tube  and  dish  under  the  receiver 
of  an  air  pump  and  pumping  out  the  air,  the 
mercury  will  sink  in  the  tube. 

The  mercury  held  up  in  the  tube  by  the  air 
weighs  about  15  pounds.  The  mercury  there- 
fore presses  down  in  the  tube  with  a  force  of  15 
pounds  per  square  inch.  Since  the  mercury  is 
held  up  in  the  tube  by  the  downward  pressure 
of  air  on  the  mercury  in  the  dish,  which  pressure 
is  transmitted  through  the  mercury  in  the  dish 
to  the  base  of  the  mercury  in  the  tube,  this  pres- 
Flg 35  _A  sure  of  the  air  must  amount  to  15  pounds  per 
Torricellian  square  inch.  That  is,  the  air  presses  down  upon 
each  square  inch  of  the  earth's  surface  with  a 
pressure  of  15  pounds.  Or,  in  other  words,  the  weight  of 
a  column  of  air  one  square  inch  in  cross  section  and  reach- 
ing from  the  earth  as  high  as  the  atmosphere  extends  is  15 
pounds.  This  pressure  of  15  pounds  to  the  square  inch  is 
often  spoken  of  as  a  pressure  of  one  atmosphere.  This  figure 
is  only  approximate,  varying  with  the  amount  of  water  vapor 
in  the  air,  and  with  the  altitude  of  the  place  where  the 
measurement  is  made. 


THE   ATMOSPHERE 


99 


This  experiment  with  the  tube  was  first  tried  by  Torricelli, 
and  the  vacuum  above  the  mercury  in  the  tube  is  therefore 
often  called  a  Torricellian  vacuum. 

Still  another  way  to  show  this  atmospheric  pressure  is  to 
place  a  hollow  tube,  as  a  straw,  in  a  glass  of  soda  water,  and 
then  remove  with  the  mouth  the  air  from 
the  upper  end  of  the  tube.  The  fluid  is  then 
forced  up  the  tube  by  the  outside  pressure. 
This  is  commonly  called  "  suction,"  but  in 
reality  the  soda  is  pushed  up  the  tube  by  the 
pressure  of  the  air  on  the  surface  of  the  soda. 

An  inverted  tube  filled  with  mercury  regis- 
ters the  pressure  of  the  air,  and  as  this  pres- 
sure changes,  the  height  of  the  mercury 
changes.  Such  a  device  is  called  a  barometer 
(Fig.  36).  By  means  of  a  barometer  one  can 
readily  determine  the  daily  changes  in  atmos- 
pheric pressure,  due  to  temperature  changes 
and  the  presence  of  water  vapor  in  varying 
amounts. 

Use  of  barometer  in  foretelling  weather 
changes.  Water  vapor  is  lighter  than  air. 
Since  water  vapor  in  the  air,  by  crowding  out 
the  heavier  gases,  makes  the  air  lighter,  and 
thereby  makes  its  pressure  less,  the  mercury 
falling  in  the  barometer  tube  (called  a  falling 
barometer)  indicates  an  increasing  amount  of 
water  vapor  in  the  air,  and  hence  a  prob- 
ability of  rain.  Thus  changes  of  air  pressure 
are  frequently  accompanied  by  the  changes  of  weather  with 
which  we  are  familiar. 

Generally,  in  an  area  where  the  air  pressure  is  much  lower 

WEED    CHEMISTRY 7 


FIG.  36.  — A 
barometer. 


100 


CHEMISTRY   IN   THE   HOME 


than  the  average  for  that  region,  the  weather  is  warm  and 
cloudy ;  while  in  areas  where  the  pressure  is  higher  than  the 
average,  the  weather  is  apt  to  be  cold  and  clear.  What  we 
ordinarily  call  a  storm  is  simply  an  area  of  low  pressure  and 
rainy  or  snowy  weather. 

It  has  been  found  by  experienced  observers  in  the  United 
States  that  these  related  weather  conditions  of  pressure, 


Isothermal  Lines 

Isobaric  Lines 

Storm  Track      f 

Storm  Cente 

Clear    o     Partly  Cloudy 

Rain  R.    Snow  S.      • 

Arrows  point  in  the  direction  wind  is  bid 

Shaded  areas  show  region  of  precipitatio 

during  the  last  12  hours. 


FIG.  37.  —  Path  of  a  storm  across  the  United  States. 

temperature,  and  cloudiness  do  not  long  remain  in  one  place, 
but  move  across  the  country  in  a  general  direction  from  west 
to  east.  By  a  careful  study  of  the  usual  paths  and  velocity 
of  these  areas,  it  has  become  possible  to  foretell  the  approach 
of  a  storm.  The  government  publishes  each  day  a  map  of 
the  country  with  these  conditions  marked  on  it,  and  by 
its  use  it  is  possible  to  trace  the  path  of  a  storm,  day  by 


THE   ATMOSPHERE  i  '•'  ,  •'  ilOl 


day,  and  to  estimate  when  it  ma-jN'be  ;  exacted  llb'/ 
us  (Fig.  37). 

Absolute  and  relative  humidity.  Air  always  contains 
water  vapor  resulting  from  evaporation.  The  weight  of 
water  vapor  actually  present  in  a  given  volume  of  air  is 
called  its  absolute  humidity.  This  is  usually  expressed  in 
grains  per  cubic  foot. 

The  ability  of  air  to  dissolve  water  increases  with  the  rise 
of  its  temperature.  When  air  contains  all  the  water  vapor  it 
can  hold  at  a  given  temperature,  it  is  said  to  be  saturated. 
The  ratio  of  the  absolute  humidity  to  the  amount  necessary 
to  saturate  the  air  at  a  given  temperature  is  called  the  relative 
humidity.  It  is  measured  in  per  cent. 

Suppose  we  find  by  actual  experiment  that  there  are  3.99 
grains  of  water  present  in  one  cubic  foot  of  the  air  in  the 
laboratory.  This  would  be  the  absolute  humidity.  We 
find  the  temperature  to  be  70°  F.  Now  from  a  table  (see 
Laboratory  Manual)  we  find  that,  at  70°  F.,  7.98  grains  of 
water  per  cubic  foot  are  required  to  saturate  the  air.  If 
7.98  grains  of  water  are  required  to  saturate  the  air,  and  we 
have  but  3.99  grains  present,  the  air  is  3.99  -r-  7.98  =  \ 
saturated.  The  air  is  50%  saturated,  or,  the  relative  hu- 
midity is  50%. 

Dew  point,  dew,  and  frost.  If  the  temperature  of  the 
air  is  lowered,  its  capacity  for  holding  water  vapor  is  lessened, 
and  therefore  its  relative  humidity  is  raised.  If  the  cooling 
is  sufficient,  the  relative  humidity  will  reach  100%  (satu- 
rated), and  further  cooling  will  result  in  condensation  of  a 
part  of  the  vapor.  In  this  way  dew  and  frost  are  formed. 

The  temperature  when  condensation  of  water  vapor  from 
the  air  begins  is  called  the  dew  point.  This  is  the  cause  of 
the  "  sweating  "  of  ice-water  pitchers,  and  the  condensation 


102  CHEMISTRY   IN   THE   HOME 

Of-  wife  on-  the  HvmetbW  -panes  in  the  winter.  Shopkeepers 
are  often  annoyed  by  this  condensation  of  water  on  the  glass 
of  their  show  windows,  and  to  prevent  it,  they  direct  blasts 
of  air  from  an  electric  fan  against  the  glass.  This  keeps  it 
clear.  Why? 

Effect  of  humidity  on  our  comfort.  A  good  complexion 
is  one  of  the  things  that  we  all  admire,  and  a  good  complexion 
depends  largely  upon  the  humidity  of  the  air.  English  girls 
are  famous  for  the  beauty  of  their  skin,  and  England  is 
famous  too  for  its  fogs  and  humidity.  The  connection  is 
this.  If  the  relative  humidity  sinks  too  low,  water  is  taken 
from  the  skin  by  the  air,  and  the  result  is  a  clry  parched  skin. 
If  you  travel  in  those  parts  of  our  country  where  the  air  is 
noted  for  its  dryness,  you  will  find  that  the  skin  of  the  natives 
presents  a  dry,  leathery  appearance. 

When  the  humidity  is  low,  not  only  the  skin,  but  the 
mucous  membranes  give  up  water  to  the  air,  and  we  suffer 
in  consequence.  In  winter,  you  know  how  often  you  go 
home  and  after  being  in  the  house  a  little  while,  begin  to 
complain  of  a  dry  throat  and  a  general  feeling  of  discomfort. 
Often  this  is  laid  to  steam  heat.  Steam  heat  is  no  different 
from  any  other  kind  of  heat,  the  difficulty  being  that  the 
relative  humidity  is  50%  out  of  doors,  and  that  it  is  a  cold 
day.  This  cold  air  is  warmed  in  the  house  to  70  °  F.  but  no 
additional  water  is  added  to  it.  The  relative  humidity  will 
of  course  become  less,  although  the  absolute  humidity  re- 
mains the  same.  In  consequence,  the  dry  air  takes  mois- 
ture from  our  nostrils  and  throats,  and  we  soon  feel  the 
effects. 

The  remedy  naturally  is  to  add  water  to  the  air.  If  you 
use  steam  heat,  hang  a  wet  towel  on  the  radiator,  and  notice 
how  quickly  the  room  feels  more  comfortable.  Furnaces 


THE   ATMOSPHERE  103 

commonly  have  a  water  pan  provided,  so  that  the  warm  air 
passes  over  water  on  its  way  to  warm  the  rooms.  This  is 
right  in  principle,  but  the  pans  are  usually  made  so  small 
that  they  do  not  help  much.  Not  only  ourselves,  but  even 
the  furniture  feels  the  effect  of  this  excessive  dryness  of  the 
air.  The  glue  that  holds  our  chairs  becomes  so  dried  out 
that  it  cracks,  and  soon  the  chair  falls  to  pieces. 

An  example  may  make  this  matter  clearer.  Suppose  that, 
when  the  temperature  outside  is  20°  F.,  the  absolute  humid- 
ity is  1.235  grains  of  water  per  cubic  foot,  or  the  relative 
humidity  is  100%.  If  now  we  warm  this  air  to  70°  F.,  the 
amount  of  water  vapor  remains  unchanged,  but  since  at  70°  F. 
a  cubic  foot  of  air  can  dissolve  7.980  grains  of  water,  the 
relative  humidity  has  fallen  to  13%,  an  amount  so  low  that 
we  suffer.  The  relative  humidity  in  our  houses  should  be 
from  50%  to  65%  for  comfort  and  health. 

One  advantage  of  a  dry  climate  is  the  comfort  that  is 
experienced  on  a  hot  day.  You  have  no  doubt  on  some  sum- 
mer days  felt  hot  and  sticky,  even  though  the  temperature 
was  not  abnormally  high.  This  is  due  to  the  fact  that  if 
the  relative  humidity  is  very  high,  the  perspiration  does  not 
readily  evaporate.  That  heat  is  required  to  evaporate  liquids 
rapidly  is  a  matter  of  common  knowledge.  If  the  relative 
humidity  is  low,  the  perspiration  quickly  evaporates.  This 
requires  heat,  and  this  heat  comes  from  our  bodies,  and  thus 
we  are  cooled.  In  Arizona,  with  the  thermometer  at  100°  F. 
you  will  be  more  comfortable  than  in  New  York  at  90°  F., 
owing  to  the  dryness  of  the  air  in  Arizona. 

Preparing  nitrogen  from  the  air.  If  we  float  a  piece  of 
phosphorus,  placed  on  a  crucible  cover  supported  on  a  cork, 
in  a  dish  of  water,  set  fire  to  the  phosphorus,  and  then  invert 
a  bottle  over  it,  the  phosphorus  burns  for  a  while  and  then 


104  CHEMISTRY   IN   THE   HOME 

goes  out  (Fig.  38).  A  white  solid,  an  oxide  of  phosphorus, 
results,  and  this  solid  being  soluble  in  water,  dissolves,  and 
water  then  rises  inside  the  bottle. 

When  we  measure  the  amount  of  gas  remaining,  we  find 
that  about  one  fifth  of  the  air  has  disappeared.  One  of  the 
constituents  of  the  air  has  been  burned  out.  From  your 
experiment  on  oxygen  you  will  infer  that  the  gas  removed 
is  oxygen.  The  gas  remaining  behaves  in  an  entirely  different 

manner  from  air.  It  is  inert, 
will  not  support  burning,  we 
cannot  live  in  it,  nor  will  metals 
rust  in  it. 

When   we   burn   phosphorus 
in   the    air,    we    cannot    easily 
regain  the  oxygen  from  the  com- 
pound   formed.      If,    however, 
FIG.  38.  —  Removal  of  oxygen     we  heat  mercury  in  the  air,  it 

combines  with  the  oxygen  and 

changes  to  a  red  rust.  If  this  rust  is  heated  to  a  higher 
temperature,  it  breaks  up  into  mercury  and  oxygen,  thus 
giving  us  a  means  of  separating  air  into  its  two  main  con- 
stituent gases,  oxygen  and  nitrogen. 

Composition  of  the  air.  The  inert  gas  remaining  after 
the  oxygen  has  been  removed  is  called  nitrogen.  It  is  im- 
portant, because  it  is  one  of  the  constituents  of  an  important 
class  of  foods.  The  composition  of  the  air  is  about  one  fifth 
oxygen  and  four  fifths  nitrogen.  The  air  also  contains  about 
four  parts  per  10,000  of  carbon  dioxide,  a  varying  amount  of 
water  vapor,  and  small  amounts  of  ammonia  and  certain  rare 
gases,  as  argon  and  neon. 

Proofs  that  air  is  not  a  compound,  but  a  mixture.  The 
oxygen  and  nitrogen  in  air  are  not  chemically  combined. 


THE   ATMOSPHERE  105 

That  the  air  is  a  mixture  is  shown  in  many  ways,  some  of 
which  are  given  below. 

When  air  dissolves  in  water,  if  it  were  a  compound,  it 
would  dissolve  as  air,  that  is,  the  proportion  of  oxygen  in 
the  dissolved  gas  would  be  the  same  as  in  air.  Instead,  we 
find  that  dissolved  air  contains  twice  as  great  a  percentage 
of  oxygen  as  the  original  air.  This  is  because  the  oxygen  and 
nitrogen  dissolve  in  the  water  as  separate  gases,  and  not 
as  a  compound. 

When  pure  water  boils,  the  resulting  steam,  if  condensed, 
has  the  same  composition  as  the  original  water.  If  air  were 
a  compound,  it  would  do  the  same,  but  when  we  liquefy  air, 
and  then  allow  it  to  boil,  the  nitrogen  boils  away  first,  leaving 
the  oxygen. 

The  composition  of  air  varies  somewhat,  while  the  com- 
position of  any  compound  is  always  the  same. 

Air  essential  to  man.  Air  is  just  as  essential  to  man  as 
food.  He  absorbs  daily,  through  his  lungs,  about  26  ounces 
of  oxygen  from  the  air,  and  exhales  about  31.5  ounces  of 
carbon  dioxide  during  the  same  time.  The  inhaled  oxygen 
dissolves  in  the  red  coloring  matter  of  the  blood  (haemoglo- 
bin), entering  into  a  loose  chemical  combination  with  it, 
and  is  so  carried  to  the  cells  of  the  body,  where  it  is  used  in 
the  oxidation  of  foods  and  protoplasm,  thus  making  possible 
the  development  of  heat  and  other  forms  of  energy.  Thus 
every  movement  of  the  body,  the  maintenance  of  the  tem- 
perature of  the  body,  and  even  our  power  to  think  depend 
on  the  oxygen  we  obtain  from  the  air. 

The  carbon  dioxide  which  results  from  this  oxidation  in  the 
cell  is  carried  back  to  the  lungs  by  the  blood  and  exhaled, 
consequently  the  air  that  leaves  the  lungs  is  of  a  different 
composition  from  that  inhaled.  The  amount  of  oxygen  has 


106 


CHEMISTRY   IN   THE   HOME 


been  decreased  from  21%  to  about  16%  by  volume,  the 
percentage  of  carbon  dioxide  has  increased  from  4  to  about 
430  parts  per  10,000  in  volume,  and  a  large  amount  of  water 
vapor  has  been  added,  as  well  as  small  amounts  of  various 
organic  waste  materials. 

Ventilation.  Exhaled  air  is  generally  warmer  and  there- 
fore lighter  than  inhaled  air,  and  therefore  rises.  In  order 
to  ventilate  our  houses  properly,  we  should  see  that  fresh 

air  is  admitted  to  the  bottom  of 
the  room,  and  that  the  impure 
hot  upper  air  is  drawn  off.  It  is 
therefore  better,  when  we  wish  to 
ventilate  a  room,  to  open  both  the 
top  and  the  bottom  of  the  window 
(Fig.  39).  A  capacity  of  one  thou- 
sand cubic  feet  of  air  per  person  in 
an  ordinary  room,  with  the  usual 
ventilation  through  doors,  chim- 
neys, and  cracks  around  the  win- 
dows, will  ordinarily  keep  the  air 
in  good  condition. 

The  carbon  dioxide  in  pure  air 
is  about  4  parts  in  10,000.     In  a 
room  such  as  a  school  recitation 
FIG.  39.  —  Ventilation  by  a  de-   room,  it  may  rise  to  20  parts,  but 
dire'ctTaJf d  *  ^^  *   this  is  evidence  of  serious  organic 
contamination  and  the  air  is  unfit 

to  breathe.  The  New  York  Board  of  Education  allows,  in 
designing  school  buildings,  30  cubic  feet  of  air  per  minute 
per  pupil. 

The  notion  that  many  people  have  that  night  air  is  in- 
jurious is  unfounded.  Circumstances  may  make  some  par- 


THE   ATMOSPHERE 


107 


ticular  night  air  impure,  but  in  general  the  air  at  night  is  just 
the  same  as  during  the  day,  and  ventilation  at  night  is  just 
as  important  as  ventilation  during  the  day.  To  sleep  in  a 
strong  draft  may  not  be  advisable,  but  to  sleep  in  a  room 
without  good  ventilation  is  to  wake  the  next  morning  feeling 
dull,  depressed,  and  out  of  sorts  with  the  world. 

What  is  known  in  history  as  the  "  Black  Hole  of  Calcutta  " 
is  an  illustration  of  what  the  lack  of  ventilation  may  cause. 
During  the  mutiny  in  India,  146  English  prisoners  were 
confined  in  a  room  20  feet  square,  with  only  two  small  win- 
dows, which  were  obstructed  by  a  veranda.  As  a  result  the 
next  morning  only  23  were  alive.  The  others  had  been 
suffocated  by  the  lack  of  oxygen.  The  same  thing  happens 
in  a  less  degree  when  we  live  and  sleep  in  improperly  venti- 
lated rooms.  It  is  a 
slow  but  sure  method 
of  poisoning,  since 
pure  air  is  essential 
for  our  well-being. 

The  air  cycle. 
Since  not  only  ani- 
mals but  plants  re- 
quire oxygen  and  ex- 
hale carbon  dioxide, 
and  since  every  fire  uses  up  the  oxygen  of  the  air,  we  may 
well  wonder  why  it  has  not  long  since  become  exhausted 
(Fig.  40).  The  explanation  is  found  in  the  way  that  plants 
grow.  Almost  every  compound  found  in  the  vegetable 
world  contains  carbon,  and  this  carbon  comes  largely  from 
the  carbon  dioxide  of  the  air.  Plants  take  in  the  carbon 
dioxide  exhaled  by  animals,  and  that  produced  by  combus- 
tion, and  use  the  carbon  in  forming  wood  and  other  com- 


Oxygen  of 
the  air 

Oxygen 
is 
given  out 

Breathed  in 
by  animals 

Used  in 
combustion 

Plants 
use 
carbon 
dioxide 

1 

I 

Carbon  dioxide 
is  given  out 

FIG.  40.  —  Cycle  of  carbon  and  oxygen. 


108  CHEMISTRY   IN   THE   HOME 

pounds.  The  oxygen  set  free  in  this  process  passes  off  once 
more  into  the  air.  In  this  way  the  amount  of  oxygen  in 
the  air  is  maintained  almost  constant. 

SUMMARY 

Air  can  be  cooled  and  compressed  to  a  colorless  liquid. 

A  pressure  of  one  atmosphere  is  a  pressure  of  15  pounds  to  the  square 

inch. 

The  weight  of  13  cubic  feet  of  air  is  about  one  pound. 
The  barometer  at  sea  level  usually  stands  at  about  30  inches. 
A  falling  barometer  indicates  the  approach  of  a  storm. 
A  rising  barometer  indicates  clearing  weather. 
Absolute  humidity  is  the  amount  of  water  vapor  present  in  the  air. 

It  is  usually  expressed  in  grains  per  cubic  foot. 
Relative  humidity  is  the  ratio  between  the  amount  of  water  vapor 

actually  present  in  the  air  to  the  amount  required  to  saturate 

the  air  at  that  temperature. 

The  composition  of  the  air  is  about  \  oxygen  and  f  nitrogen. 
Air  is  a  mixture,  not  a  compound. 
Ventilation  is  essential  to  health. 

Exercises 

1.  Carbon  dioxide  is  harmless.     Why  then  is  a  large  percentage 
in  the  air  of  rooms  regarded  as  objectionable? 

2.  Show  by  a  diagram  how  you  would  ventilate  your  sleeping 
room. 

3.  Would  it  be  an  advantage  to  us  to  have  the  air  pure  oxygen  ? 
Explain. 

4.  There  is  little  vegetation  in  a  large  city,  and  the  city  uses  large 
amounts  of  oxygen  from  the  air.     Why  do  the  citizens  not  die  as  a 
result  of  the  exhaustion  of  the  oxygen  of  the  air  ? 

6.   Could  plants  live,  if  there  were  no  animals  ? 

6.  Could  animals  live,  if  there  were  no  plants? 

7.  Name  two  sources  of  the  carbon  dioxide  in  the  air.     Of  the 
moisture  in  the  air. 

8.  How  is  the  composition  of  the  air  kept  constant? 


CHAPTER  X 
FORMULAS,   EQUATIONS,   AND   VALENCE 

Atomic  weight  defined.  Every  atom  of  an  element  is 
just  like  every  other  atom  of  the  same  element  (p.  53). 
Every  atom  of  hydrogen  weighs  just  the  same  as  every  other 
atom  of  hydrogen.  The  symbol  H  then  means  not  only 
one  atom  of  hydrogen,  but  also  a  definite  weight  of  hydro- 
gen. Chemists  are  able  to  determine  the  comparative 
weights  of  atoms  of  different  elements.  The  oxygen  atom, 
for  example,  weighs  16  times  as  much  as  the  hydrogen  atom. 
The  atom  of  carbon  is  12  times  as  heavy  as  the  hydrogen 
atom.  These  comparative  weights  we  call  atomic  weights. 
(See  table,  p.  378.) 

As  the  hydrogen  atom  is  the  lightest  one  known,  its  weight 
may  be  called  one,  and  the  weight  of  the  other  atoms  expressed 
in  terms  of  it.  To  say  that  the  atomic  weight  of  chlorine  is 
35.5  means  that  one  atom  of  chlorine  weighs  35.5  times  as 
much  as  one  atom  of  hydrogen.  Atomic  weight  may  be 
defined  as  the  weight  of  one  atom  of  any  element  compared  to 
the  weight  of  one  atom  of  hydrogen.1 

Molecular  weight  defined.  The  formula  of  water,  H2O, 
shows  that  water  is  made  up  of  two  atoms  of  hydrogen  and 
one  atom  of  oxygen.  If  we  know  the  atomic  weight  of 
hydrogen  to  be  one,  and  that  of  oxygen  to  be  sixteen,  we  can 

1  Since  in  determining  these  comparative  atomic  weights  chemists 
usually  work  with  oxygen,  oxygen  (16)  is  often  taken  as  the  practi- 
cal standard. 

109 


110  CHEMISTRY   IN   THE    HOME 

calculate  that  a  molecule  of  water  weighs  18  times  as  much 
as  an  atom  of  hydrogen,  the  weight  of  which,  you  will  remem- 
ber, is  our  standard.  This  number,  18,  is  called  the  molecular 
weight  of  water.  Molecular  weight  may  be  defined  as  the 
weight  of  one  molecule  of  a  compound  as  compared  with  the 
weight  of  one  atom  of  hydrogen.  It  can  always  be  found  by 
adding  together  the  weights  of  the  atoms  that  compose  a 
molecule.  Sugar  has  the  formula  C^H^Ou.  The  12  atoms 
of  carbon  weigh  12  X  12  =  144,  the  22  atoms  of  hydrogen, 
22,  and  the  11  atoms  of  oxygen,  11  X  16  =  176,  making  a 
total  of  342  for  the  molecular  weight  of  cane  sugar. 

Naming  compounds.  To  learn  how  to  name  the  thousands 
of  inorganic  chemical  compounds  would  at  first  seem  like  a 
difficult  task,  yet  by  the  aid  of  a  few  simple  rules  the  difficulty 
vanishes.  First,  we  must  remember  that  in  chemical  for- 
mulas the  symbol  of  the  more  metallic  element  is  usually 
written  first.  When,  then,  we  examine  such  a  formula  as 
KC1,  we  may  not  know  what  element  the  symbol  K  stands 
for,  but  we  may  be  reasonably  sure  that  it  is  the  symbol 
of  the  more  metallic  element. 

Naming  binary  compounds.  The  simplest  compounds 
are  of  course  those  made  up  of  only  two  elements,  such  as 
copper  chloride,  CuCl2,  potassium  chloride,  KC1,  etc.  Such 
compounds  as  these  are  easily  named.  All  that  you  have  to 
do  is  to  name  the  more  metallic  element  first,  and  then  follow 
it  by  the  name  of  the  less  metallic  element,  so  modified  as  to 
end  in  -ide.  In  the  formula  CuCl2  we  know  that  the  symbol 
Cu  means  copper,  and  since  this  is  given  first  it  is  the  metallic 
part  of  the  compound.  Cl  means  chlorine,  and  this  name  we 
change  so  as  to  end  in  -ide.  The  name  of  the  compound 
is  therefore  copper  chloride.  Similarly,  NaCl  is  sodium 
chloride. 


FORMULAS,   EQUATIONS,   AND  VALENCE        111 

The  fact  that  the  name  of  a  compound  ends  in  -ide  tells 
you  that  it  must  be  made  up  of  two  elements,  and  two  ele- 
ments only.  Sodium  oxide,  for  example,  must  be  made 
up  of  sodium  and  oxygen;  potassium  iodide,  of  potassium 
and  iodine. 

It  often  happens  that  elements  combine  in  more  than  one 
proportion.  Thus,  hydrogen  and  oxygen  combine  to  form 
the  compounds  H2O  and  H2O2.  Both  of  these  compounds 
may  be  called  oxide  of  hydrogen.  To  distinguish  between 
them  the  prefix  per-,  meaning  the  higher  state  of  oxidation, 
is  used  in  naming  the  H2O2. 

Sometimes  the  Greek  prefixes,  mono-,  one ;  di-,  two ;  tri-, 
three,  etc.,  are  used  to  distinguish  between  different  com- 
pounds of  the  same  elements,  as  CO,  carbon  monoxide,  and 
CO2,  carbon  dioxide. 

Naming  chemical  compounds.  We  can  name  most  other 
inorganic  compounds  if  we  know  the  name  of  the  acid  from 
which  they  are  prepared.  All  acids  contain  hydrogen,  and 
the  symbol  of  the  hydrogen  is  always  given  first  in  writing 
their  formulas.  Nitric  acid  is  HXO3  and  sulphuric  acid, 
H2SO4.  In  many  chemical  changes  involving  acids,  the 
hydrogen  of  the  acid  is  replaced  by  a  metal.  In  this  way 
a  new  compound  called  a  salt  is  formed. 

When  sodium  and  nitric  acid  interact,  the  hydrogen  of  the 
acid  is  replaced  by  sodium,  and  a  new  compound,  NaN03,  is 
obtained.  Since  this  compound  was  made  from  nitric  acid, 
and  also  contains  sodium,  its  name  should  suggest  both  of 
these.  It  is  called  sodium  nitrate,  the  name  being  obtained 
by  naming  the  metal  and  following  it  by  a  modified  name  of 
the  acid.  The  name  of  Xa2SO4,  since  it  is  prepared  from 
sulphuric  acid,  would  be  sodium  sulphate.  In  the  same 
way  phosphoric  acid  produces  phosphates,  and  oxalic  acid, 


112  CHEMISTRY   IN   THE    HOME 

oxalates.  The  question  then  comes,  why  do  we  not  call  the 
compound  made  by  replacing  the  hydrogen  of  hydrochloric 
acid  with  sodium,  sodium  hydrochlorate,  instead  of  sodium 
chloride  ?  This  seeming  exception  to  the  rule  arises  because 
the  name  falls  under  two  rules.  We  may  either  call  the  com- 
pound sodium  hydrochlorate,  in  accordance  with  the  rule 
just  given,  or,  since  it  is  a  compound  composed  of  two  ele- 
ments, sodium  chloride,  in  accordance  with  our  first  rule. 
The  simpler  name  is  commonly  used. 

In  the  above  cases  of  compounds  derived  from  acids,  you 
will  notice  that  all  the  names  of  the  acids  end  in  -ic.  Some 
acids  have  names  ending  in  -ous,  and  compounds  formed  from 
them  have  names  ending  in  -ite.  Thus,  when  the  hydrogen  in 
nitrous  acid,  HNO2,  is  replaced  by  sodium,  we  have  the 
compound  NaNC^.  This  is  called  sodium  nitrite. 

Radicals  explained.  When  the  hydrogen  of  an  acid  is 
replaced  by  a  metal,  the  other  atoms  do  not  as  a  rule  sep- 
arate, but  tend  to  stick  together  and  act  as  a  single  atom. 
Thus,  if  we  take  the  hydrogen  away  from  sulphuric  acid 
by  means  of  sodiumr  the  sulphur  and  oxygen  of  the  acid  do 
not  separate,  but  act  as  a  single  atom,  forming  the  com- 
pound Na2SO4. 

Such  groups  of  atoms  we  call  radicals.  They  are  not 
capable  of  existing  free  and  uncombined,  but  always  exist  in 
combination  with  some  other  element.  A  few  of  them  are  so 
important  that  they  have  been  given  names.  One  of  them, 
OH,  is  called  hydroxyl.  It  can  combine  with  elements  to 
form  compounds  called  hydroxides.  Thus  NaOH  is  named 
sodium  hydroxide.  This  compound  has  the  ending  -ide, 
although  it  has  three  elements  in  it,  instead  of  only  two,  as 
the  name  would  indicate. 

One  very  important  metallic  radical  is  called  ammonium, 


FORMULAS,   EQUATIONS,   AND  VALENCE         113 


NH4.  Like  other  radicals,  it  cannot  exist  alone,  but  its 
compounds  are  common.  In  many  ways  it  acts  like  the 
metal  sodium,  and  so  we  call  it  a  metallic  radical.  Chemists 
call  the  compound  NH4OH  ammonium  hydroxide,  but  you 
know  it  under  the  name  of  ammonia  water. 

Important  acid  formulas.  In  order  to  name  chemical 
compounds  we  must  be  able  to  recognize  and  name  the  sym- 
bols of  the  elements  and  to  know  the  radicals  of  the  common 
acids.  The  formulas  of  a  few  acids  and  salts  are  given  below 
and  should  be  memorized. 


SODIUM  SALTS  DERIVED  FROM 

ACIDS 

THESE  ACIDS 

Name 

Formula 

Name 

Formula 

Sodium 

Nitric 

HNO3 

nitrate 

NaN03 

Sulphuric 

H2S04 

sulphate 

Na2SO4 

Hydrochloric 

HC1 

chloride 

NaCl 

Carbonic 

H2C03 

carbonate 

Na2CO3 

Phosphoric 

H3P04 

phosphate 

Na3P04 

Acetic 

HC2H302 

acetate 

NaC2H302 

Chemical  equations.  It  is  often  desirable  to  express  the 
facts  of  a  chemical  change  in  the  form  of  an  equation.  The 
fact  that  one  molecule  of  oxygen  combines  with  two  mole- 
cules of  hydrogen,  thus  producing  two  molecules  of  water, 
may  be  expressed  in  the  brief  equation : 

2  H2  +  O2  ->  2  H2O 

Chemical  equations  are  much  like  those  of  algebra.  You 
must  have  as  many  atoms  of  each  element  on  one  side  of  the 
equation  as  on  the  other.  You  may  multiply  both  sides  by 
the  same  quantity.  You  may  add  the  same  quantity  to  each 


114  CHEMISTRY   IN   THE   HOME 

side.  You  will  notice,  though,  that  we  do  not  use  an  equality 
sign  between  the  two  members,  but  an  arrow.  This  is  be- 
cause we  wish  to  indicate  in  which  direction  the  reaction 
occurs.  Thus,  the  above  equation  does  not  mean  that  water 
becomes  hydrogen  and  oxygen,  but  that  hydrogen  and  oxygen 
become  water. 

In  some  cases  the  chemical  change  may  take  place  in  either 
direction,  in  which  case  we  use  a  double  arrow,  as  in  the  fol- 
lowing example.  Calcium  carbonate  (marble),  when  heated, 
will  give  off  carbon  dioxide,  forming  calcium  oxide  (quick- 
lime). If  the  carbon  dioxide  is  not  allowed  to  escape,  the 
calcium  oxide  will  absorb  it,  and  be  converted  into  calcium 
carbonate.  The  double  arrow  in  the  equation  shows  that 
the  reaction  goes  on  in  both  directions. 

CaCO3  ±£  CaO  +  CO2 

You  must  not  imagine  that  every  chemical  change  that 
you  can  represent  by  an  equation  will  take  place.  You 
must  know  that  the  chemical  change  involved  is  possible 
before  you  attempt  to  write  the  equation. 

In  writing  equations  it  is  necessary  to  balance  them,  that 
is,  to  see  that  there  are  the  same  number  of  atoms  of  each 
element  on  each  side  of  the  equation.  Suppose  you  have 
prepared  hydrogen  by  the  action  of  hydrochloric  acid  upon 
zinc,  and  wish  to  write  the  equation  representing  the  action 
between  them.  You  start  by  putting  down  all  the  com- 
pounds used,  and  the  compounds  formed,  thus : 

Zn  +  HC1  ->  ZnCl2  +  H2 

Evidently  this  is  not  complete,  as  we  have  two  atoms  of 
chlorine  on  the  right-hand  side,  and  but  one  on  the  left.  You 
must  use  two  molecules  of  hydrochloric  acid  to  obtain  these 


FORMULAS,   EQUATIONS,   AND  VALENCE        115 

two  atoms  of  chlorine,  and  will  then  have  two  atoms  of  hydro- 
gen (one  molecule)  left.     The  complete  equation  is : 

Zn  +  2  HC1  -+  ZnCl2  +  H2 

It  will  be  good  practice  for  you  to  balance  the  incomplete 
equations  given  below : 

NaOH  +  H2SO4  ->  Na2SO4  + 
NaOH  +  H2S04  ->  NaHSO4  + 
CaCO3  +  HC1  ->  CaCl2  +  CO2  -f 
A1203  +  H2S04  -+  A12(S04)3  + 
CaO  +  HC1  ->  CaCl2  + 

Valence  explained.  One  of  the  puzzling  things  to  be- 
ginners in  chemistry  is  to  know  how  many  atoms  of  each 
element  to  include  when  writing  the  formula  of  a  compound. 
For  example,  you  have  learned  that  copper  oxide  is  a  com- 
pound of  copper  with  oxygen.  .This,  of  itself,  is  not  enough 
to  enable  you  to  write  the  formula,  as  it  might  be  CuO,  CuO2, 
Cu2O,  etc.  You  must  know  how  many  atoms  of  oxygen  and 
how  many  of  copper  are  present.  A  knowledge  of  what 
chemists  call  valence  will  often  enable  you  to  write  the  correct 
formula. 

The  formulas  of  hydrochloric  acid,  HC1 ;  water,  H2O ; 
ammonia,  H3N  ;  and  marsh  gas,  H^C,1  have  been  determined 
by  actual  analysis  in  the  laboratory.  An  examination  of 
these  formulas  shows  that  chlorine,  oxygen,  nitrogen,  and 
carbon  differ  in  their  ability  to  combine  with  hydrogen 
atoms  and  form  compounds  with  it.  An  atom  of  chlorine 
is  able  to  hold,  or  combine  with,  only  one  atom  of  hydrogen. 
An  atom  of  oxygen  can  hold  two,  an  atom  of  nitrogen  three, 

1  The  formula  of  marsh  gas  is  generally  written  CH4.  In  this 
discussion  it  is  written  H4C  to  make  it  agree  with  HC1  and  H2O. 
The  same  thing  is  true  of  ammonia.  It  is  commonly  written  NH3. 

WEED   CHEMISTBY 8 


116 


CHEMISTRY   IN   THE    HOME 


an  atom  of  carbon  four,  hydrogen  atoms.  This  power  of  the 
atom  of -an  element  to  combine  with,  or  replace,  one,  two,  or 
more  hydrogen  atoms  is  called  its  valence. 

Let  us  call  the  valence  of  hydrogen  one,  taking  it  as  the 
standard.  Chlorine  will  also  have  a  valence  of  one,  as  it  can 
combine  with  but  one  hydrogen  atom.  Oxygen  must  have  a 
valence  of  two,  as  it  will  combine  with  two  hydrogen  atoms. 
The  valence  of  nitrogen  must  be  three,  and  the  valence  of 
carbon,  four,  for  similar  reasons. 

A  simple  way  of  thinking  of  valence  is  to  think  of  wooden 
blocks  having  one,  two,  or  more  hooks  placed  in  them. 

Imagine  that  you  have  two 
kinds  of  wooden  blocks, 
one  red  and  the  other  blue 
(Fig.  41),  each  block  hav- 
ing one  hook.  Should  you 
attempt  to  hook  red  blocks 
and  blue  blocks  together, 

FIG.  41.  — Diagram  to  illustrate  it  Would   be  easy  to  hook 

valence,  one  red  block  and  one  blue 

block  together.  There  you  would  have  to  stop.  You 
could  not  hook  a  second  red  block  upon  the  blue  one,  for 
there  would  be  no  hook  vacant  on  which  to  hang  it.  If, 
though,  you  had  a  third  kind  of  block,  a  yellow  one  having 
two  hooks,  you  could  hang  a  red  block  on  to  each  hook  of  the 
yellow  block,  thus  forming  a  set  of  three  blocks.  If  now  you 
will  call  the  blue  blocks  chlorine  atoms,  the  red  ones  hydrogen 
atoms,  and  the  yellow  ones  oxygen  atoms,  you  will  see  how  the 
molecules  of  hydrochloric  acid  and  of  water  are  put  together. 
It  seems  to  be  true  that  every  hook  of  an  element  must  be 
used.  Carbon  has  four  hooks.  We  cannot  have  such  a 
compound  as  H3C,  as  that  would  leave  a  hook  unused. 


FORMULAS,   EQUATIONS,   AND  VALENCE         117 

You  must  be  sure  to  understand  that  these  hooks  are  only 
imaginary.  We  do  not  think  for  an  instant  that  real  atoms 
have  real  hooks  coming  from  them.  To  the  beginner,  though, 
the  question  of  valence  is  puzzling,  and  to  think  of  actual 
blocks  and  hooks  helps  to  make  the  matter  clear.  Chemists 
speak  not  of  hooks  but  of  bonds.  In  the  future,  then,  we  must 
not  say  that  carbon  has  four  hooks,  but  that  carbon  has 
four  bonds,  or,  that  its  valence  is  four.  We  may  also  say 
that  it  is  tetravalent.  An  element  with  three  bonds  is  triva- 
lent;  one  with  two  bonds,  bivalent;  and  with  one  bond, 
univalent. 

Variable  valence.  The  subject  of  valence  is  not  quite  so 
simple  as  you  might  think  from  the  above.  Elements  some- 
times change  their  valence.  Thus  the  valence  of  iron  may 
be  two  or  three,  and  we  have  in  consequence  two  iron  chlo- 
rides, FeCl2  and  FeCl3.  The  valences  of  elements  are  given 
in  the  table  on  page  378. 

Writing  formulas  of  salts.  Having  learned  the  formulas 
of  some  of  the  common  acids,  and  the  valence  of  some  of  the 
common  metals,  you  can  write  the  formulas  of  their  com- 
pounds without  trouble.  Let  us  suppose  you  wish  to  write 
the  formula  of  sodium  sulphate.  You  know  that  it  must 
contain  sodium  atoms,  combined  with  the  SO4  radical.  The 
question  now  is,  how  much  of  each  must  be  taken.  The 
lormula  of  sulphuric  acid  is  H2SO4.  Since  the  864  radical  is 
able  to  hold  two  atoms  of  hydrogen,  its  valence  must  be  two. 
The  valence  of  sodium  being  one,  the  SC>4  radical  must  be 
able  to  combine  with  two  atoms  of  sodium  instead  of  two 
atoms  of  hydrogen.  The  formula,  then,  must  be  NasSC^. 

How  to  find  the  valence  of  an  element.  You  can  of  course 
work  this  same  process  backward  in  order  to  find  out  the 
valence  of  an  element,  provided  you  know  the  formula  of 


118  CHEMISTRY   IN   THE   HOME 

some  one  of  its  compounds.  The  formula  of  potassium 
phosphate  is  K3PO4.  Knowing  that  the  valence  of  PO4  is 
three,  and  that  three  atoms  of  potassium  will  combine  with 
it,  you  know  that  the  total  valence  of  the  three  atoms  of 
potassium  must  be  three,  or  that  the  valence  of  one  atom 
must  be  one.  Potassium  must  then  have  a  valence  of  one 
or  is  univalent. 

The  formula  of  aluminium  oxide  is  A12O3.  Since  the 
valence  of  oxygen  is  two,  three  atoms  of  it  must  have  six 
bonds.  The  two  atoms  of  aluminium  must  therefore  have 
six  bonds,  or  each  atom  must  have  three  bonds,  that  is,  the 
valence  of  aluminium  is  three. 

Empirical  and  rational  formulas.  Compounds  contain- 
ing carbon  often  have  a  large  number  of  atoms  in  them. 
The  formula  of  cane  sugar  (sucrose) ,  for  example,  is  C^H^Oii. 
Such  a  formula  as  this,  giving  only  the  number  of  atoms  in  a 
molecule,  is  called  an  empirical  formula.  Such  a  formula 
does  not  give  us  all  of  the  information  that  we  need ;  for  if 
you  again  think  of  your  wooden  blocks  with  hooks,  you  will 
see  that  it  would  be  possible  to  link  such  a  large  number  of 
blocks  together  in  many  ways,  and  still  have  all  of  the  hooks 
used. 

It  is  not  until  a  chemist  knows,  not  only  the  number  of 
atoms  in  the  molecule,  but  how  these  atoms  are  arranged, 
that  he  really  knows  much  about  the  compound.  When  we 
have  found  out  the  actual  arrangement  of  the  atoms,  we  can 
then  draw  a  diagram  that  will  show  not  only  the  number,  but 
the  arrangement  of  the  atoms.  Such  a  diagram  (formula) 
we  call  a  graphic  formula.  The  empirical  formula  of  acetic 
acid  is  C2H4O2.  Since  acetic  acid  has  four  hydrogen  atoms 
in  it,  you  would  expect  its  radical  to  be  €202,  that  this  radical 
would  have  a  valence  of  four,  and  that  the  formula  of  sodium 


FORMULAS,   EQUATIONS,   AND   VALENCE        119 

acetate  would  be  Xa4C2O2.  Instead  of  this,  the  acid  radical 
is  C2H3O2,  its  valence  one,  and  the  formula  of  sodium  acetate 
Xar2H3O2.  An  examination  of  the  graphic  formula  will 
explain  why  this  is  so. 

II  O 


H  — C    —  C  — O  — H 


H 

GRAPHIC  FORMULA  OF  ACETIC  ACID. 

You  will  notice  that  three  of  the  four  atoms  of  hydrogen  are 
united  to  a  carbon  atom,  while  the  fourth  is  united  to  an 
oxygen  atom.  The  hydrogen  atom  that  is  united  to  the 
oxygen  is  easily  replaced,  while  the  others  are  not. 

We  find  the  same  thing  true  in  the  case  of  other  organic 
acids.  They  all  contain  many  hydrogen  atoms,  some  com- 
bined with  carbon,  and  some  united  to  oxygen.  We  find  that 
only  those  united  to  the  oxygen,  or  rather  those  that  form 
part  of  the  group  C— O— O— H  (called  the  carboxyl  group) 
are  replaceable  by  metals  to  form  salts.  An  ordinary  empiri- 
cal formula  would  not  show  this,  hence  the  importance  of 
the  graphic  formula.  To  show  this  difference  in  the  hydro- 
gen atoms,  the  formula  of  acetic  acid  is  better  written 
HC2H3O2,  instead  of  C2H4O2. 

How  graphic  formulas  are  found.  To  determine  these 
graphic  formulas  is  often  a  matter  of  great  difficulty.  It  can 
often  be  done  by  breaking  up  a  complex  compound  into 
simpler  ones,  studying  the  arrangement  of  the  atoms  in 
these,  and  then  studying  the  way  in  which  these  simple 
compounds  unite  to  form  the  original  substance. 

In  many  cases  how  the  atoms  are  arranged  is  not  known, 


120  CHEMISTRY   IN  THE   HOME 

and  in  these  cases  it  is  almost  impossible  to  reproduce  the 
compound  in  the  laboratory.  When  the  graphic  formula  is 
known,  the  chemist,  in  many  cases,  can  go  into  the  labora- 
tory and  make  the  compound,  because  he  knows  how  it  is 
built. 

The  manufacture  of  synthetic  indigo  was  made  possible 
only  after  chemists  had  determined  the  graphic  formula  of 
the  natural  indigo.  After  it  could  be  made  in  the  laboratory, 
it  was  years  before  it  could  be  made  cheaply.  To-day  most 
of  the  blue  cloth  of  commerce  is  dyed  with  synthetic  indigo, 
made  not  by  nature  in  the  indigo  plant,  but  by  man.  It  is 
not  an  imitation,  but  real  indigo. 

A  similar  thing  is  being  done  in  the  case  of  rubber,  but 
the  work  is  not  yet  so  far  advanced.  It  is  possible  now  to 
make  rubber  in  the  laboratory,  but  the  artificial  product 
costs  much  more  than  the  natural.  It  is  probable,  though, 
that  in  time  chemists  will  be  able  to  cheapen  the  process, 
and  that  synthetic  rubber  will  become  an  article  of  com- 
merce. 

These  synthetic  products  must  not  be  confused  with  imita- 
tions. To  determine  that  the  flavor  of  vanilla  is  due  to  a 
substance  called  vanillin,  to  make  that  synthetically,  and 
to  sell  it  for  flavoring  purposes,  is  legitimate.  But  to  sell 
vanillin,  colored  with  caramel,  and  call  it  "  genuine  vanilla 
extract  "  is  a  fraud. 

Chemical  problems.  A  knowledge  of  atomic  and  molec- 
ular weights  is  indispensable  to  the  manufacturing  chemist. 
A  simple  problem  taken  from  your  laboratory  work  will 
illustrate  this.  You  have  prepared  hydrogen  by  the  action 
of  hydrochloric  acid  on  zinc.  Suppose  you  wish  to  know 
how  much  acid  will  be  required  to  dissolve  40  grams  of 
zinc.  By  first  writing  the  equation  and  then  calculating 


FORMULAS,   EQUATIONS,   AND  VALENCE        121 

the  molecular  weights,  it  is  possible  to  state  a  proportion 
that  will  give  you  the  desired  information. 

Zn  +  2  HC1  ->  ZnCl2  +  H2 
65+73        ->•      136  +  2 
138  =  138 

FACTORS  PRODUCTS 

Weight  of  1  atom  of  Zn  65  Zn  -  65 

H=    1  2C1  =  71 

G  =  35.5  1*36 

Molecular  weight  of  HC1  36.5  Molecular  weight  of  ZnCl2    136 

Weight  of  2  molecules  of  HC1  73      Weight  of  1  molecule  of  H,>  2 

Total  weight  used  138          Total  weight  obtained      138 

The  equation  tells  us  that  65  grams  of  zinc  will  require 
73  grams  of  hydrochloric  acid  to  dissolve  it :  then  40  grams 
of  zinc  will  require  x  grams  of  hydrochloric  acid. 
65  :  73  ::  40  :  x 

Solving  the  proportion,  x  =  44.9  grams  of  acid  required. 

SUMMARY 

Atomic  weight  is  the  weight  of  one  atom  of  an  element  compared  to 

the  weight  of  one  atom  of  hydrogen. 
Molecular  weight   is   the  weight  of   one  molecule  of  a  substance 

compared  to  the  weight  of  one  atom  of  hydrogen. 
Valence  denotes  the  number  of  hydrogen  atoms  that  one  atom  of  an 

element  can  combine  with,  or  replace. 
A  radical  is  a  group  of  atoms  that,  in  reactions,  usually  acts  like  one 

atom.     A  radical  cannot  exist  free. 

Naming  binary  compounds  :    Compounds  containing  only  two  ele- 
ments have  the  more  metallic  element  named  first,  followed 
-  by  the  name  of  the  other  element  so  modified  as  to  end  in-ide. 
Naming  salts  from  -ic  acids  :  If  the  name  of  an  acid  ends  in  -ic,  the 

name  of  the  compound  made  from  it  ends  in  -ate. 
Naming  salts  from  -ous  acids  :  If  the  name  of  an  acid  ends  in  -ous, 

the  name  of  the  compound  made  from  it  ends  in  -ite. 


122  CHEMISTRY   IN   THE   HOME 

Exercises 

1.  Find  the  molecular  weight  of  NaOH,  K20,  NaHC03,  HC1. 

2.  Name  NaOH,  KOH,  NaCl,  CuO,  HgO,  CuS,  PH3,  NH3. 

3.  Name  CO,  C02,  P203,  P205,  FeCl2,  FeCl3. 

4.  The  valence  of  iron,  Fe,  is  3.     The  valence  of  oxygen,  O,  is  2. 
What  is  the  formula  of  iron  oxide  ? 

6.  The  formula  of  potassium  chloride  is  KC1.  The  formula  of 
tartaric  acid  is  H2C4H406.  What  is  the  formula  of  potassium 
tartrate  ? 

6.  The  formula  of  silver  nitrate  is  AgN03.    The  formula  of  nitric 
acid  is  HN03.     What  is  the  valence  of  silver? 

7.  Balance  the  following  equations  : 

HC1  +  NaOH  ->  NaCl  +  ? 
H2S04  +  Na20  -+  NaHS04  +  ? 
HN03  +  K2C03  ->  KN03  +  C02  +  ? 

8.  How  many  grams  of  hydrogen  can  be  obtained  by  decom- 
posing 9  grams  of  water  ?     How  many  grams  of  oxygen  ? 

9.  How  many  grams  of  chlorine  and  hydrogen  will  be  required 
to  combine  and  form  80  grams  of  hydrochloric  acid  ? 

10.  What  is  the  percentage  composition  of  water  ?  (This  is  the 
same  thing  as  asking  how  many  grams  of  oxygen  and  hydrogen  will 
be  required  to  form  100  grams  of  water.) 


CHAPTER  XI 
CHLORINE 

How  electrolysis  is  used  by  chemists.  Nature  has  re- 
vealed to  us  many  of  her  secrets,  but  there  are  many  still  to 
be  discovered.  One  of  these  is  the  cause  of  the  changes  that 
take  place  in  the  appearance  and  properties  of  elements  when 
they  unite  to  form  compounds.  A  notable  example  of  this 
is  the  compound  that  we  all  know  so  well,  common  salt.  If 
table  salt  is  melted  in  a  suitable  vessel,  and  an  electric  current 
then  passed  through  it,  the  salt  is  decomposed  into  two 
elements,  sodium  and  chlorine. 

Neither  of  the  two  elements,  sodium  and  chlorine,  obtained 
from  salt  by  electrolysis,  resembles  salt  in  the  slightest.  So- 
dium is  a  silvery  white,  soft,  light  metal,  while  chlorine  is  a 
bad-smelling,  poisonous  gas.  You  will  remember  that  water 
can  be  decomposed  in  this  same  way.  The  electric  current 
is  of  great  use  to  chemists  in  pulling  many  other  compounds 
to  pieces.  Many  metals,  as  aluminium  and  calcium,  are 
obtained  by  passing  an  electric  current  through  one  of  their 
fused  compounds. 

The  preparation  of  chlorine.  There  are  easier  ways  of 
obtaining  chlorine  in  the  laboratory  than  by  decomposing 
salt.  One  of  the  common  acids  that  you  have  used  is  called 
hydrochloric  acid,  or,  to  use  its  old  name,  muriatic  acid. 
This  acid  has  the  formula  HC1,  that  is,  it  is  composed  of 
chlorine  and  hydrogen.  You  know  that  oxygen  has  a  great 

123 


124 


CHEMISTRY   IN   THE   HOME 


liking  for  hydrogen.  If,  then,  we  add  to  hydrochloric  acid 
some  substance  that  will  easily  give  up  oxygen  (an  oxidiz- 
ing agent),  the  oxygen  will  unite  with  the  hydrogen,  leaving 
the  chlorine  free.  Any  good  oxidizing  agent  can  be  used. 
Potassium  chlorate,  hydrogen  peroxide,  or  potassium  per- 
manganate will  serve  the  purpose,  as  you  will  find  in  the 
laboratory.  We  usually  use  manganese  dioxide,  which  is 


FIG.  42.  —  Preparation  of  chlorine. 

inexpensive.     It  is  also  insoluble,  and  so  the  action  is  slow, 
which  is  an  advantage. 

To  make  chlorine,  place  manganese  dioxide  in  a  flask,  and 
add  hydrochloric  acid  (Fig.  42) .  To  hasten  the  action  heat 
the  flask.  A  greenish  yellow  gas  is  given  off,  which  is  chlorine. 
If  we  bubble  this  gas  through  water,  the  water  becomes  col- 
ored, showing  that  the  gas  dissolves  in  it.  Chlorine  is  there- 
fore not  collected  like  oxygen,  for  the  chlorine  would  dissolve 
in  the  water.  Chlorine  is  collected  by  displacement  of  air. 
Simply  place  the  end  of  the  delivery  tube  from  which  chlorine 
is  flowing,  close  to  the  bottom  of  a  bottle,  and  the  chlorine 


CHLORINE  125 

will  fill  the  bottle,  driving  out  the  lighter  air.     The  color  of 
the  gas  enables  us  to  tell  when  the  bottle  is  filled  with  it. 

An  illustration  of  completing  a  chemical  equation.  The 
formula  of  manganese  dioxide  is  MnO2.  That  is,  one  mole- 
cule contains  one  atom  of  the  metal  manganese  and  two 
atoms  of  oxygen.  Only  one  of  the  oxygen  atoms  is  easily 
given  up,  that  is,  only  one  of  them  can  be  used  for  oxidizing 
purposes.  Let  us  write  the  formula,  then,  as  MnO(O),  so 
as  to  show  the  difference  between  the  oxygen  atoms.  Now 
we  are  ready  to  work  out  the  equation  that  shows  us  just 
how  much  MnO2  and  HC1  we  must  use.  The  one  atom  .of 
oxidizing  oxygen  can  combine  with  two  atoms  of  hydrogen, 
and  to  furnish  these  two  hydrogen  atoms  we  must  use  two 
molecules  of  hydrochloric  acid,  or : 

MnO(O)  +  2  HC1  ->  MnO  +  H2O  +  2  Cl 

The  two  atoms  of  chlorine  will  at  once  combine  to  form 
one  molecule,  so  it  would  be  better  to  write  C12  rather  than 
2  Cl.  The  MnO  that  is  left  is  soluble  in  hydrochloric  acid, 
and  as  we  have  plenty  of  this  present,  a  second  equation 
takes  place : 

MnO  +  2  HC1  ->  MnCl2  +  H2O 

These  two  changes  take  place  simultaneously,  so  that  we 
would  ordinarily  write  only  the  complete  equation  obtained 
by  adding  these  two : 

MnO(O)  +  2  HC1  ->  MnO  +  C12  +  H2O 

MnO  +  2  HC1  -+  MnCl2  +  H2O 

Mn02  +  MnO  +  4  HC1  ->  MnO  +  MnCl2  +  C12  +  2  H2O 

As  the  MnO  occurs  on  both  sides  of  the  equation,  we  may 
cancel  it,  which  leaves  as  the  final  equation  : 

Mn02  +  4  HC1  ->  MnCl2  +  2  H2O  +  C12 


126  CHEMISTRY   IN   THE   HOME 

If  we  had  used  potassium  chlorate,  a  similar  change  would 
have  taken  place : 

KC103  +  6  HC1  ->  KC1  +  3  H2O  +  3  C12 

Preparation  and  use  of  bleaching  powder.  One  other 
method  of  obtaining  chlorine  is  worth  remembering.  You 
have  doubtless  used  at  home  bleaching  powder,  called  also 
chloride  of  lime.  This  is  a  white  powder,  obtained  by  passing 
chlorine  over  lime,  when  the  lime  combines  with  large  quan- 
tities of  the  chlorine. 

CaO  +  C12  -*  CaOCl2 

If  an  acid  is  added  to  the  bleaching  powder,  the  chlorine 
is  again  set  free,  and  this  is  an  easy  way  of  obtaining 
chlorine  gas  in  the  home. 

CaOCl2  +  2  HC1  ->  CaCl2  +  H2O  +  C12 

Properties  of  chlorine.  Chlorine  is  a  heavy  gas  of  a 
greenish  yellow  color,  and  of  an  exceedingly  disagreeable 
odor.  It  affects  the  mucous  membranes,  as  the  lining  of 
the  throat  and  nose,  producing  the  sensations  of  a  bad  cold. 
It  is  poisonous,  and  care  should  be  taken  not  to  inhale  it. 
Should  you  suffer  from  its  effects  at  any  time,  inhaling  the 
vapor  of  alcohol  will  bring  some  relief.  It  is  soluble  in  water, 
one  volume  of  water  dissolving  two  volumes  of  the  gas,  at 
ordinary  temperature. 

Chlorine  combines  readily  with  metals.  This  can  be 
easily  shown  by  heating  a  copper  wire  and  plunging  it  into 
a  jar  of  the  gas.  Dense  yellow  fumes  of  copper  chloride  will 
appear,  and  the  energy  of  the  chemical  change  is  so  great 
that  the  copper  is  heated  to  a  glowing  red  heat. 

Gold  is  sometimes  obtained  from  its  ores  by  grinding  the 
ore  to  a  very  fine  powder,  and  then  shaking  this  powder 


CHLORINE  127 

with  chlorine  water.  The  gold  combines  with  the  chlorine, 
forming  gold  chloride,  AuCl2.  This  dissolves  in  the  water, 
is  drawn  off,  and  the  gold  obtained  from  it. 

When  a  lighted  candle  is  placed  in  a  bottle  of  chlorine, 
the  flame  becomes  very  smoky  and  of  a  peculiar  reddish 
hue.  The  chlorine  disappears,  and  a  black  deposit  forms 
on  the  sides  of  the  jar.  If  you  will  recall  that  candle  wax  is 
a  compound  of  hydrogen  and  carbon,  you  can  explain  what 
has  happened.  Hydrogen  easily  combines  with  chlorine, 
while  carbon  does  not.  Tests  show  that  the  gas  left  in  the 
jar  is  an  acid  and  that  the  black  deposit  will  burn.  The 
result  of  the  chemical  change  in  the  bottle  is  that  hydro- 
chloric acid  is  formed  and  that  carbon  is  set  free.  Other 
compounds  of  carbon  and  hydrogen  behave  in  the  same 
way  when  burned  in  chlorine. 

Chlorine  can  easily  be  condensed  to  a  liquid,  and  is  often 
sold  in  this  form,  the  liquid  being  contained  in  steel  cylinders 
that  can  withstand  great  pressure.  It  combines  readily 
with  hydrogen,  forming  hydrochloric  acid.  For  this  reason, 
the  water  solution  of  chlorine  cannot  be  kept  for  any  length 
of  time,  as  the  hydrogen  of  the  water  combines  with  the 
chlorine,  forming  hydrochloric  acid  and  liberating  oxygen. 

2  H20  +  2  C12  ->  4  HC1  +  02 

Uses  of  chlorine.  Chlorine  has  two  great  uses,  both  of 
which  are  interesting  to  us.  It  is  used  as  a  bleaching  agent 
and  as  a  disinfectant.  Its  bleaching  power  is  shown  only 
when  the  article  to  be  bleached  is  wet.  This  is  because  the 
chlorine  combines  with  the  hydrogen  of  the  water,  leaving 
oxygen.  This  oxygen  is  very  energetic.  This  is  often  true 
of  elements  at  the  instant  that  they  are  set  free,  and,  to  ex- 
press this  condition,  we  say  that  the  element  is  in  the  nascent 


128 


CHEMISTRY   IN   THE   HOME 


state.  This  energetic  oxygen  oxidizes  the  color  that  we 
wish  to  destroy.  Not  all  colors  will  be  bleached,  but  only 
those  that  can  be  easily  oxidized.  Thus,  printer's  ink  con- 
tains carbon,  and  since  carbon  is  not  easily  oxidized  at  low 
temperatures  printer's  ink  is  not  bleached  by  chlorine. 

Bleached  cotton  has  been  through  a  process  at  the  mills  as 
illustrated  in  Figure  43.     The  unbleached  cotton  is  on  a  roll 


TO 


: 


B       S       B       S         C  W         W 

FIG.  43.  —  Process  of  bleaching  cloth. 

04).  It  passes  through  bleaching  vats  (BB)  which  contain 
a  thin  paste  of  bleaching  powder.  Following  each  bleaching 
bath  the  cloth  passes  into  a  weak  acid  (SS).  Sodium 
sulphite  (C)  neutralizes  any  chlorine  in  the  cloth.  After 
thorough  washing  in  water  (WW),  the  cloth  is  dried  and 
ironed  (H)  and  the  bleached  cloth  rolled  on  a  drum  (F). 

The  second  use  of  chlorine,  that  of  a  disinfectant,  is  de- 
pendent upon  the  same  facts.  It  oxidizes  the  offensive 
matter.  For  this  use  bleaching  powder  is  suitable.  A 
little  of  the  powder,  scattered  in  a  place  where  offensive  odors 
are  being  generated,  slowly  decomposes  and  oxidizes  the 
objectionable  matter,  thus  destroying  the  odor. 

Use  of  Javelle  water  in  the  laundry.  Possibly  you  have 
never  had  the  experience  of  sending  a  shirt  or  a  shirtwaist 
to  the  laundry,  and  having  it  come  back  dazzlingly  white, 


CHLORINE  129 

only  to  find  on  wearing  it  that  the  cloth  has  had  its  strength 
destroyed.  This  "  tendering  "  of  the  cloth  is  due  to  the 
incorrect  use  of  chlorine  as  a  bleach.  If  chloride  of  lime  is 
mixed  with  washing  soda,  a  clear  solution  of  sodium  hypo- 
chlorite  (Javelle  water)  results.  This  is  often  used  by  laun- 
dries, and  in  the  home,  as  a  bleach,  as  it  gives  off  chlorine 
readily.  Properly  used,  it  is  not  objectionable.  But  if  a 
quantity  of  it  is  poured  on  a  tubful  of  clothes,  some  of  the 
clothes  receive  more  than  their  share,  and  the  strength  of 
the  cloth  is  consequently  destroyed.  Some  materials,  as 
silk  and  wool,  cannot  be  bleached  with  chlorine,  as  the  fiber 
would  be  turned  yellow  and  destroyed. 

Ink  eradicators.  One  of  the  common  ink  eradicators  is 
made  of  sodium  hypochlorite.  This  is  rubbed  on  the  ink 
spot  that  is  to  be  removed,  and  the  excess  blotted  off.  A 
weak  acid  solution  is  then  put  on  the  ink.  Chlorine  is  set 
free,  and  this  bleaches  the  ink.  Many  stains  will  yield  to 
the  same  treatment.  Care  must  be  used  not  to  have  the 
solution  so  strong  that  the  fiber  of  the  cloth  will  be  weakened. 

SUMMARY 

Preparation  of  chlorine  :  Chlorine  is  prepared  by  the  electrolysis  of 
sodium  chloride,  and  by  the  oxidation  of  hydrochloric  acid. 

Properties  of  chlorine :  Chlorine  is  a  heavy  gas,  greenish  yellow  in 
color,  soluble  in  water,  and  active  chemically. 

Uses  of  chlorine :  Chlorine  is  used  for  bleaching  and  disinfecting. 
Javelle  water  (sodium  hypochlorite)  is  a  good  bleaching  agent. 

Exercises 

1.  Why  does  not  chlorine  bleach  printer's  ink? 

2.  Is  Javelle  water  suitable  to  remove  a  stain  from  colored  calico  ? 

3.  Will  chlorine  bleach  all  writing  inks  ?    Explain. 

4.  Is  Javelle  water  a  suitable  bleach  for  a  woolen  sweater? 


CHAPTER  XII 


ACIDS,    BASES,   AND    SALTS 

A  study  of  hydrochloric  acid  as  a  typical  acid.  Many  of 
the  substances  used  in  the  household  have  a  decidedly  sour 
taste.  This  taste  is  generally  due  to  the  presence  of  some 
one  of  a  class  of  bodies  known  as  acids.  Vinegar  contains 
acetic  acid,  lemon  juice  contains  citric  acid,  while  the  small 
green  apples  that  occasionally  cause  much  trouble  to  small 

boys  contain  malic  acid.  Acids 
differ  in  many  of  their  physical 
properties.  Hydrochloric  acid, 
for  instance,  is  a  gas ;  acetic  acid 
is  a  liquid;  and  oxalic  acid  is  a 
solid.  They  all,  however,  have 
certain  chemical  properties  in 
common.  We  shall  now  study  a 
typical  acid,  hydrochloric  acid, 
and  see  if  we  can  from  this  study 
find  what  are  the  chemical  char- 
acteristics of  acids. 

Preparation.  A  mixture  of 
equal  volumes  of  hydrogen  and 
chlorine,  when  exposed  to  sun- 
light, combines  with  explosive  violence,  forming  a  colorless 
gas  which  we  name  hydrochloric  acid. 

This  is  an  expensive  and  undesirable  »way  of  forming  the 
acid.  A  much  better  laboratory  method  is  to  place  in  a 

130 


FIG.  44.  —  Preparation  of  hy- 
drochloric acid. 


ACIDS,  BASES,  AND  SALTS         131 

flask,  provided  with  a  delivery  tube,  a  quantity  of  salt 
(Fig.  44).  Then  add  some  sulphuric  acid  and  warm  gently. 
A  colorless  gas,  called  hydrochloric  acid,  is  given  off  in  large 
quantities,  and  may  be  collected  in  bottles  by  displacement 
of  air.  It  cannot  be  collected  by  displacement  of  water 
owing  to  its  very  great  solubility  in  water.1 

NaCl  +  H2S04  ->  NaHS04  +  HC1  f 

The  hydrochloric  acid  that  we  ordinarily  use  in  the  labo- 
ratory is  a  solution  of  this  gas  in  water.  This  is  a  colorless 
liquid  having  a  specific  gravity  of  1.13,  and  contains  about 
33%  of  real  hydrochloric  acid.  It  often  goes  under  the  name 
of  muriatic  acid. 

Properties.  Hydrochloric  acid  is  corrosive  in  its  action, 
dissolving  the  oxides  of  most  of  the  metals,  with  the  forma- 
tion of  chlorides,  as  the  following  equation  shows : 

ZnO  +  2  HC1  ->  ZnCl2  +  H2O 

It  is  too  powerful  an  acid  to  be  suitable  for  most  household 
uses.  Old  iron  stains,  however,  that  resist  almost  every 
other  form  of  treatment,  may  be  removed  from  cloth  by  soak- 
ing the  stain  in  a  dilute  solution  of  hydrochloric  acid,  and 
then  washing  the  fabric  well. 

Hydrochloric  acid,  in  common  with  all  other  acids,  causes 
most  dyes  to  change  color.  Should  you  get  any  of  it  upon 
your  dress,  a  red  spot  may  be  the  result.  The  original  color 
usually  can  be  restored  by  adding  ammonia,  and  then  rins- 
ing with  clean  water. 

Typical  properties  of  acids.  We  have  used  hydrochloric 
acid  in  the  laboratory  to  prepare  hydrogen  by  its  action  on 

1  At  the  room  temperature  1  c.c.  of  water  will  dissolve  450  c.c. 
of  hydrochloric  acid  gas  weighing  0.8  gram.  This  gives  1.5  c.c. 
of  concentrated  hydrochloric  acid  solution. 

WEED    CHEMISTRY 9 


132  CHEMISTRY   IN   THE   HOME 

zinc.  We  have  also  used  sulphuric  acid  and  magnesium, 
and  found  that  they  set  hydrogen  free.  Since  similar  re- 
sults are  obtained  from  using  some  other  acids  and  some 
other  metals,  we  may  conclude  that  the  action  of  acids  on 
metals  is,  in  general,  to  set  hydrogen  free, 

2  HC1  +  Zn  ->  ZnCl2  +  H2 
H2S04+Mg->MgS04  +  H2 

Another  property  common  to  all  acids  is  their  action  on 
certain  colors.  From  one  of  the  lichens  a  blue  dye  called 
litmus  is  obtained.  If  an  acid  is  added  to  this  blue  litmus, 
the  blue  changes  to  red.  If,  then,  we  wish  to  know  whether 
any  liquid  contains  an  acid,  we  may  add  a  little  blue  litmus 
to  it.  If  the  litmus  changes  to  red,  we  know  that  an  acid  is 
present.  Since  litmus  indicates  the  presence  of  an  acid, 
chemists  call  it  an  indicator. 

Let  us  sum  up  the  properties  of  acids.  They  are  bodies 
having  a  sour  taste.  They  all  contain  hydrogen,  and  this 
hydrogen  is  usually  united  to  nonmetallic  elements.  Metals 
can  replace  this  hydrogen,  setting  it  free.  They  all  turn  blue 
litmus  red.  They  are  generally  soluble  in  water. 

Typical  properties  of  bases.  Another  class  of  bodies  has 
properties  which  are  opposite  to  those  of  acids.  We  call  this 
class  bases.  They  have  a  bitter  or  alkaline  taste,  they  turn 
red  litmus  blue,  and  feel  soapy  to  the  touch.  Chemically 
they  are  hydroxides  of  metals.  One  of  the  most  important 
bases  is  sodium  hydroxide.  A  solution  that  turns  red  litmus 
blue  is  said  to  have  an  alkaline  reaction.  Strong  soluble 
bases,  like  sodium  hydroxide,  are  often  called  alkalies. 

Sodium  hydroxide.  Soda  lye,  or  sodium  hydroxide, 
NaOH,  is  one  of  the  sodium  compounds  familiar  to  house- 
keepers. It  has  the  power. of  combining  with  almost  all 


ACIDS,   BASES,   AND   SALTS  133 

forms  of  grease  to  form  soap,  and  so  is  of  use  in  cleaning  out 
greasy  sinks  and  pipes,  being  more  powerful  in  its  action  than 
the  washing  soda  so  commonly  used  for  this  purpose.  It 
must,  however,  be  handled  with  some  care,  as  its  action  on 
the  skin  is  corrosive.  It  is  a  white,  deliquescent  substance. 
It  may  be  prepared  by  the  action  of  sodium  on  water. 

2  Na  +  2  H2O  ->  2  NaOH  +  H2 

Sodium  hydroxide  is  prepared  on  a  commercial  scale  from 
quicklime  which  is  mixed  with  water  until  a  milklike  fluid 
is  obtained.  To  this  a  solution  of  washing  soda  is  added. 
The  two  chemicals  react,  and  the  calcium  carbonate  that  is 
formed,  being  insoluble,  settles  to  the  bottom  of  the  tank. 
The  sodium  hydroxide  solution  is  then  drawn  off  and  evapo- 
rated, leaving  a  white,  deliquescent  solid. 

CaO  +  H2O  ->  Ca(OH)2 
Ca(OH)2  +  NaaCQs  -*  CaCO3  +  2  NaOH 

Much  sodium  hydroxide  is  manufactured  by  the  electrolysis 
of  common  salt  and  at  the  same  time  chlorine  is  produced. 
Large  quantities  of  sodium  hydroxide  are  used  in  the  prepa- 
ration of  soap. 

Neutralization  and  the  formation  of  salts.  When  an  acid 
and  a  base  are  mixed  in  solution,  chemical  action  takes  place. 
The  hydrogen  of  the  acid  combines  with  the  OH  (hydroxyl) 
of  the  base,  and  water  is  formed.  The  metal  of  the  base 
and  the  acid  radical  then  combine  and  form  a  body  known 
as  a  salt.  Thus,  sodium  hydroxide,  mixed  with  acetic  acid, 
forms  water -and  sodium  acetate. 

NaOH  +  HC2H302  ->  H2O  +  NaC2H3O2 

You  must  carefully  distinguish  between  salt,  which  is 
sodium  chloride,  and  a  salt,  whiph  is  one  of  a  class  of  bodies. 


134  CHEMISTRY   IN   THE    HOME 

When  an  acid  and  a  base  combine,  the  characteristic 
properties  of  both  are  destroyed.  The  new  substances  are 
usually  neutral  to  the  litmus  test,  and  their  taste  is  neither 
acid  nor  alkaline.  This  chemical  change  is  called  neutral- 
ization. 

Not  only  the  hydroxides,  but  also  the  carbonates  of  metals 
will  neutralize  acids.  If  sodium  carbonate,  called  washing 
soda,  is  mixed  with  an  acid,  carbon  dioxide  and  water  are 
formed,  and  a  salt  is  left.  If  hydrochloric  acid  is  used, 
sodium  chloride  will  be  formed. 

Na^COs  +  2  HC1  ->  2  XaCl  +  H2O  +  CO2 

Exact  neutralization.  To  neutralize  an  acid  exactly  by 
means  of  a  base  requires  some  care,  but  it  can  readily  be 
done  with  the  aid  of  litmus.  If  to  hydrochloric  acid  in  a 
flask  a  few  drops  of  litmus  solution  are  added,  the  liquid 
becomes  red  in  color.  If  now  a  solution  of  sodium  hydrox- 
ide is  added,  shaking  well  after  each  addition  so  as  to  mix  the 
liquids  thoroughly,  the  acid  and  base  will  combine,  forming 
water  and  sodium  chloride.  When  just  enough  sodium 
hydroxide  has  been  added  to  exactly  neutralize  the  acid, 
the  litmus  will  change  to  a  violet  color,  showing  that  neither 
acid  nor  base  is  present  in  the  solution.  If  the  water  is 
now  evaporated  until  the  solution  is  saturated  and  the  dish 
is  then  set  aside,  the  sodium  chloride  will  crystallize. 

That  sodium  chloride  is  really  obtained  is  shown,  first,  by 
the  shape  of  the  crystals,  which  is  cubical,  the  same  as  that  of 
crystals  of  salt  purchased  in  the  grocery  store.  Second, 
they  have  the  well-known  salty  taste  of  common  salt. 

Composition  of  baking  powders.  The  baking  powders  so 
commonly  used  will  also  serve  to  illustrate  neutralization. 
The  common  cream  of  tartar  baking  powder  is  composed  of 


ACIDS,   BASES,   AND   SALTS  135 

potassium  hydrogen  tartrate  (cream  of  tartar),  which  has 
certain  acid  characteristics,  and  sodium  bicarbonate.  When 
these  two  are  mixed,  the  acid  part  of  the  cream  of  tartar  is 
neutralized  and  a  new  substance,  a  salt,  sodium  potassium 
tartrate  (Rochelle  salts),  is  formed.  At  the  same  time,  a 
gas,  carbon  dioxide,  is  given  off,  and  it  is  this  gas  that  makes 
the  cake  light. 

KHC4H406  +  XaHCQs  ->  KNaC4H4O6  +  H2O  +  CO2  f 

Chemically,  there  is  no  reason  why  any  acid  should  not  be 
substituted  for  the  cream  of  tartar. 

A  baking  powder  made  of  hydrochloric  acid  and  sodium 
bicarbonate  would  be  satisfactory,  except  that  it  would  be 
difficult  for  the  cook  to  mix  the  two  in  such  proportions  that 
she  could  be  sure  that  neither  would  be  present  in  excess. 
Hydrochloric  acid  and  washing  soda,  in  the  same  way,  could 
be  used,  but  would  be  open  to  the  same  objection. 

Soda  biscuits.  Those  of  you  who  have  eaten  old-fashioned 
soda  biscuits,  leavened  by  the  use  of  sour  milk  and  sodium 
bicarbonate  (saleratus),  know  that  sometimes  the  biscuits 
are  sour.  You  can  now  readily  see  why.  The  sourness  of 
milk  is  a  variable  quantity,  and  no  receipt  can  give  the 
amount  of  bicarbonate  necessary  to  neutralize  these  varying 
amounts  of  acid.  Sometimes  the  biscuits  show  yellow 
streaks  and  have  a  somewhat  soapy  taste.  This  is  due  to  an 
excess  of  saleratus,  caused  by  a  deficient  acidity  in  the  milk. 

Replacement  of  one  element  by  another.  In  the  same 
way  that  a  metal  will  replace  the  hydrogen  of  an  acid, 
other  metals  may  be  used  to  replace  the  first.  Thus  a  piece 
of  zinc  placed  in  a  solution  of  lead  nitrate  will  replace  the 
lead,  forming  lead  and  zinc  nitrate.  Similarly  copper  will 
replace  the  silver  in  silver  nitrate.  The  more  metallic  ele- 


136  CHEMISTRY   IN   THE   HOME 

ment  will  replace  the  less  metallic.  Arranging  a  few  of 
the  common  metals  in  the  order  of  their  metallic  properties 
will  tell  us  how  they  will  replace  one  another.  Magnesium, 
aluminium,  zinc,  lead,  copper,  silver,  and  gold  form  such  a 
series.  Each  metal  will  replace  all  that  come  after  it. 
Those  that  follow  are  less  metallic  than  those  which  precede. 

SUMMARY 

Hydrochloric  acid  is  made  by  the  action  of  sulphuric  acid  on  sodium 
chloride.  The  water  solution  of  it  is  in  commercial  use. 

An  acid  is  a  substance  containing  hydrogen.  As  a  rule  the  hydrogen 
is  easily  replaced  by  a  metal.  Acids  are  sour,  and  turn  blue 
litmus  red. 

A  base  is  the  hydroxide  of  a  metal.  Bases  are  caustic,  and  turn  red 
litmus  blue. 

A  salt  is  the  product  of  the  action  of  an  acid  on  a  base.  A  salt  may 
be  regarded  as  an  acid  in  which  the  hydrogen  has  been  replaced 
by  a  metal,  or,  as  a  base  in  which  the  hydroxyl  has  been  re- 
placed by  an  acid  radical. 

Neutralization  is  the  combining  of  an  acid  and  a  base,  forming 
water  and  a  salt. 

Sodium  hydroxide  is  made  by  the  reaction  of  sodium  carbonate  and 
calcium  hydroxide.  It  is  also  made  by  the  electrolysis  of  com- 
mon salt. 

Exercises 

1.  Name  two  bases  used  in  the  home. 

2.  Name  three  acids  used  in  the  home. 

3.  Why  will  a  washing  compound  often  change  the  color  of  cloth? 

4.  Why  is  ammonia  added  to  the  water  used  in  washing  windows  ? 

5.  Why  is  it  necessary  to  keep  baking  powder  in  air-tight  cans? 

6.  Given  a  colorless  liquid,  how  could  you  tell  whether  it  con- 
tained an  acid  or  a  base  ? 


CHAPTER  XIII 
SODIUM   AND   ITS   COMPOUNDS 

Properties  of  sodium.  You  will  remember  that,  by  de- 
composing fused  common  table  salt  by  electrolysis,  a  yellow- 
ish green  gas  called  chlorine  and  the  metal  sodium  are 
obtained. 

You  doubtless  think  of  a  metal  as  being  a  heavy,  hard 
substance.  This  metal  sodium,  however,  has  a  character 
entirely  different  from  that  of  an  ordinary  metal.  It  is  not 
hard,  but  so  soft  that  it  can  be  molded  in  the  fingers  like 
putty ;  nor  is  it  heavy,  in  fact  its  specific  gravity  is  so  small 
that  it  will  float  upon  \vater.  Then,  too,  we  ordinarily  think 
of  metals  as  being  exceedingly  permanent  bodies,  not  easily 
corroded  or  destroyed.  This  metal  sodium,  however,  cor- 
rodes, or  rather,  oxidizes,  so  rapidly  in  the  air  that  it  is  only 
possible  to  keep  it  in  the  metallic  state  by  preventing  the 
air  from  coming  in  contact  with  it. 

Evidently,  then,  a  chemist  has  an  entirely  different  idea 
of  a  metal  from  that  ordinarily  held.  To  a  chemist,  sodium 
is  a  typical  metal,  because  it  combines  so  energetically  with 
oxygen,  reacts  so  strongly  with  acids,  and  because  its  hydrox- 
ide is  so  strongly  alkaline. 

We  will  sum  up,  then,  the  properties  of  sodium.  It  is  a 
soft  metal  of  a  silvery  color,  very  light,  having  a  specific 
gravity  of  .935,  a  melting  point  of  207.7°  F.,  an  atomic 
weight  of  23,  is  easily  oxidized,  and  conducts  heat  and  elec- 

137 


138 


CHEMISTRY   IN   THE    HOME 


tricity  very  well.     It  is  kept  under  kerosene  or  some  other 
liquid  that  contains  no  oxygen. 

Action  of  sodium  on  water.  The  action  of  sodium  upon 
water  is  very  interesting.  If  we  fill  a  test  tube  with  water, 
invert  it  in  an  evaporating  dish  of  water,  and  then  quickly 
thrust  a  piece  of  sodium  the  size  of  a 
small  pea  under  the  mouth  of  the  test 
tube,  we  see  that  the  sodium  melts 
and  spins  around  actively,  while  the 
water  in  the  test  tube  disappears  (Fig. 
45).  If,  now,  we  place  a  finger  over 
the  mouth  of  the  test  tube,  and  bring 
it  to  a  light,  we  find  that  the  tube  is 
filled  with  an  inflammable  gas  which 
we  recognize  as  our  old  acquaintance, 
hydrogen.  If  we  wet  our  fingers  in 
the  water  in  the  evaporating  dish  and 
rub  them  together,  they  feel  soapy  or 
slippery.  On  evaporating  a  little  of  this  water,  a  white 
solid  is  obtained,  very  different  from  the  sodium  with  which 
we  started.  Evidently  the  sodium  in  setting  the  hydrogen 
free  has  combined  with  part  of  the  water. 

2  Na  +  2  H2O  ->  2  NaOH  +  H2 

Sodium  chloride  or  table  salt.  Compounds  of  sodium  are 
found  widely  distributed  in  nature,  many  rocks  and  soils 
containing  them.  Several  natural  compounds  occur  almost 
pure,  and  are  of  considerable  economic  importance.  The 
most  useful  of  these  is  sodium  chloride,  or  common  table 
salt.  This  occurs  in  very  many  localities  in  the  world  in 
large  quantities.  In  the  United  States,  it  is  found  in  enor- 
mous quantities  in  Michigan,  Utah,  and  New  York. 


FIG.  45.  —  Action  of  so- 
dium upon  water. 


SODIUM   AND    ITS   COMPOUNDS 


139 


140 


CHEMISTRY   IN   THE   HOME 


Salt  is  commonly  extracted  from  the  ground  by  sinking 
two  wells  a  short  distance  apart.  Down  one  of  these  wells 
water  is  pumped.  This  water  dissolves 
the  salt,  forming  a  strong  brine.  This 
brine  is  then  pumped  up  the  second 
well,  and  some  of  the  water  evapo- 
rated (Fig.  46).  The  salt  crystallizes, 
the  mother  liquor  is  drained  off,  and  the 
crystals  of  salt  dried.  Thus  our  com- 
mon salt  is  obtained.  The  size  of  the 
salt  crystals  is  determined  by  the  de- 
gree of  concentration  of  the  brine  and 
the  rapidity  of  the  crystallization.  The 
FIG.  47.  -  Hopper  shaped  more  siowiy  the  crystals  are  formed,  the 

crystals  of  salt.  ,  ,  T          .„   .        . 

larger  they  are.  It  will  be  interest- 
ing for  you  to  determine  what  the  crystalline  form  of  salt 
is,  by  examining  a  little  under  a  common  magnifying  glass 
(Fig.  47). 

Rock  salt  is  salt  that  is  actually  mined  from  the  ground,  just 
as  is  coal  or  iron  ore.  Its  usual  reddish  brown  color  is  due  to 
the  presence,  as  an  impurity,  of  a  small  amount  of  iron  oxide. 
Rock  salt  sometimes  occurs  in  perfectly  transparent  masses 
which  are  used  by  scientists  to  make  lenses  and  prisms. 

Rock  salt  has  been  formed  by  the  slow  evaporation  of 
large  bodies  of  salt  water  and  the  subsequent  covering  up 
of  the  deposit.  This  same  process  is  now  going  on  in  our 
country  in  the  Great  Salt  Lake.  The  water  of  this  lake  is  a 
saturated  solution  of  salt.  The  lake  itself  is  gradually  drying 
up,  and  the  salt  is  being  deposited  upon  its  shores  as  a  glisten- 
ing white  layer  some  inches  in  thickness.  If  this  process 
continues,  we  shall  have  a  bed  of  rock  salt  similar  to  those 
that  exist  in  Siberia  and  Austria. 


SODIUM   AND   ITS   COMPOUNDS     .  141 

The  ocean  is  our  great  reservoir  of  sodium  chloride.  It  is 
calculated  that  36,000,000,000,000,000  tons  of  salt  exist  in 
the  ocean,  and  much  salt  is  obtained  from  it.  At  Turks' 
Island,  for  example,  the  ocean  water  is  run  into  shallow  pans, 
and  the  water  evaporated  by  the  heat  of  the  sun.  The  result- 
ing large,  coarse  crystals  are  largely  used  in  freezing  ice  cream. 

Prepared  table  salt.  One  of  the  minor  bothers  of  the 
housewife  is  the  tendency  of  salt  to  absorb  water,  and  to 
stick  in  the  salt  cellars.  It  is  commonly  said  that  salt  is 
hygroscopic,  that  is,  gathers  water  from  the  air.  This  is 
not  true.  It  is  the  presence  of  magnesium  chloride,  MgCl2, 
a  deliquescent  substance,  and  one  of  the  common  impurities 
of  salt,  that  causes  this  moistening  of  the  salt.  It  can, 
therefore,  be  overcome  by  carefully  purifying  the  salt,  but, 
as  this  is  expensive,  another  method  is  commonly  resorted 
to.  A  small  quantity  of  starch,  or,  better,  precipitated 
chalk,  is  mixed  with  the  salt  which  has  previously  been  care- 
fully dried.  This  starch  coats  over  the  little  particles  of 
the  salt,  and  prevents  their  sticking  together. 

Uses  of  salt.  The  use  of  salt  as  a  seasoning  in  food,  and  as 
a  preservative  for  meats,  is  so  well  known  that  no  details  need 
be  given.  It  has  another  use  in  our  diet.  The  gastric  juice 
contains  a  small  amount  of  hydrochloric  acid,  and  the  chlo- 
rine for  this  comes  from  the  salt  that  we  consume.  Large 
quantities  of  salt  are  also  used  in  the  preparation  of  sodium 
carbonate,  or  washing  soda. 

Preparation  of  washing  soda.  Sodium  carbonate,  Na2CO3, 
or  washing  soda,  is  prepared  by  the  action  of  ammonium 
hydroxide  and  carbon  dioxide  upon  a  solution  of  sodium 
chloride.  This  is  known  as  the  Solvay  process. 

NH3  +  NaCl  +  CO2  +  H2O  ->  NaHCO3  +  NH4C1 


142  CHEMISTRY  IN   THE   HOME 

The  sodium  bicarbonate,  being  insoluble  in  the  liquid,  is 
deposited  as  a  crust  on  the  large  cylindrical  tanks  in  which  the 
operation  is  carried  out.  The  sodium  bicarbonate  is  filtered 
out,  and  then  heated.  This  drives  off  the  carbon  dioxide 
which  is  used  in  the  preparation  of  more  of  the  bicarbonate. 

2  NaHCO3  +  heat  ->  N^COg  +  H2O  +  CO2  f 


The  resulting  mass  is  dissolved  in  water  and  recrystallized. 
Sodium  carbonate  is  noteworthy  because,  when  it  crystallizes, 
each  molecule  combines  chemically  with  ten  molecules  of 
water  ;  that  is,  the  formula  of  crystallized  sodium  carbonate 
is  not  Na2C03,  but  Na2CO3  •  10  H2O. 

The  clean,  glassy  crystals  of  washing  soda,  then,  that  you 
buy  from  the  grocer,  are  more  than  half  water  by  weight, 
or,  to  be  exact,  286  pounds  of  this  crystallized  washing  soda 
contains  180  pounds  of  water.  On  standing,  these  glassy 
crystals  lose  most  of  their  water  of  crystallization,  and  are 
converted  into  a  dull  white  powder. 

When,  then,  you  buy  washing  soda,  do  not  too  carefully 
insist  upon  receiving  the  glassy  crystals,  but  rather  choose 
the  white  powder  that  forms  in  the  bottom  of  the  barrel,  as 
you  will  thus  receive  twice  as  much  for  your  money,  a  thing 
much  to  be  desired  in  this  day  of  high  prices. 

The  great  use  for  this  washing  soda  in  the  household  is 
in  softening  hard  water  and  as  a  cleaning  agent.  Practically 
all  washing  compounds  contain  it  and  you  are  doubtless 
familiar  with  its  use  in  cleaning  greasy  frying  pans. 

Sodium  bicarbonate,  or  baking  soda.  Not  all  of  the  sodium 
bicarbonate  is  converted  into  washing  soda;  much  of  it  is 
sold  and  consumed  under  the  name  of  baking  soda.  This 
substance  goes  under  many  other  names,  a  few  of  which  are  : 
saleratus,  cooking  soda,  sodium  hydrogen  carbonate,  and 


SODIUM   AND   ITS   COMPOUNDS  143 

sodium  acid  carbonate.  The  white  powder  is  a  mild  alkali, 
and  is  used  extensively  in  the  manufacture  of  baking  pow- 
ders. It  is  one  of  the  common  household  remedies  for  sour 
stomach. 

Borax.  Borax,  Xa2B4O7-10  H2O,  sodium  tetraborate,  is  a 
white  crystalline  substance  that  contains  ten  molecules  of 
water  of  crystallization.  It  is  used  in  soaps  as  a  mild  alkali. 
It  is  also  used  in  some  washing  compounds. 

Water  glass,  or  sodium  silicate.  Sodium  silicate,  or  water 
glass,  Na2SiO3,  is  another  sodium  compound  that  is  used  in 
the  home.  It  is  a  clear,  hard  solid,  that  dissolves  slowly  in 
water,  making  a  thick  sirup,  the  form  in  which  it  is  usually 
sold.  This  forms  an  excellent  cement,  as,  when  it  has  once 
solidified,  it  is  very  strong  and  difficult  to  dissolve. 

A  thin  solution  of  water  glass  is  often  used  to  preserve 
eggs.  It  fills  up  the  tiny  pores  in  the  shell  of  the  egg,  and 
thus  prevents  the  water  in  the  egg  from  evaporating  and 
also  prevents  any  germs  that  may  be  in  the  air  from  gaining 
access  to  the  contents  of  the  shell.  It  is  also  used  as  a  filler 
in  laundry  soap. 

Other  sodium  compounds.  Several  other  compounds  of 
sodium  are  of  industrial  importance.  Sodium  nitrate, 
NaXO3,  or  Chili  saltpeter,  is  a  white  crystal  found  in  Chili, 
and  is  used  in  large  quantities  as  a  fertilizer.  Sodium 
thiosulphate,  Na^&Os,  the  familiar  hypo  of  the  photographer, 
is  a  solvent  for  silver  bromide,  and  is  used  in  fixing  photo- 
graphic plates  and  papers. 

General  properties  of  the  sodium  salts.  The  sodium  salts 
are  practically  all  soluble  in  water,  and  form  white  crystalline 
substances.  They  are  usually  stable.  Owing  to  their  wide 
distribution,  their  cheapness,  and  their  solubility,  they  are 
widely  used  both  in  the  home  and  in  the  industries. 


144  CHEMISTRY   IN   THE    HOME 

Potassium  and  its  compounds.  The  metal  potassium  is 
very  much  like  sodium.  Whatever  sodium  will  do  chemically 
potassium  will  also  do,  but  do  it  more  energetically.  Thus, 
sodium  decomposes  water.  So  does  potassium,  but  more 
violently.  Sodium  oxidizes  in  the  air.  So  does  potassium, 
but  more  easily.  Many  potassium  salts  are  of  importance. 
We  cannot,  however,  spare  the  time  to  study  them.  It  will 
be  enough  if  you  remember  that,  generally  speaking,  potas- 
sium forms  the  same  classes  of  salts  as  sodium,  and  that 
they  have  much  the  same  properties.  The  main  difference 
between  sodium  and  potassium  salts  is  that  the  potassium 
compounds  are  usually  more  soluble. 

SUMMARY 

Sodium  is  prepared  by  the  electrolysis  of  fused  sodium  hydroxide. 

Washing  soda  is  sodium  carbonate. 

Baking  soda  is  sodium  hydrogen  carbonate. 

Table  salt  is  sodium  chloride. 

Potassium  is  much  like  sodium,  and  forms  similar  salts. 

Exercises 

1.  If  sodium  is  light  and  soft,  why  do  we  call  it  a  metal? 

2.  How  many  names  can  you  give  to  NaHC03? 

3.  Of  what  is  baking  powder  composed? 

4.  Name  three  sodium  compounds  that  you  use  in  large  amounts, 

5.  Name  one  potassium  compound  that  is  used  in  the  home. 

6.  Could  you  obtain  salt  from  sea  water  at  home? 


CHAPTER  XIV 


AMMONIA    AND    AMMONIUM    COMPOUNDS 

Preparation  of  ammonia.  Whenever  organic  material 
containing  nitrogen  compounds  decays,  a  gas  called  am- 
monia, XH3,  is  set  free.  This  is  not  a  suitable  method  to  use 
for  obtaining  it  in  the  labora- 
tory. A  better  method  is  to 
place  in  a  test  tube  a  mixture 
of  ammonium  chloride  and  some 
base,  as  sodium  hydroxide  (Fig. 
48) .  On  warming,  the  gas  am- 
monia is  given  off  in  large 
quantities,  and  can  be  collected 
by  displacement  of  air.  Any 
ammonium  compound  and  any 
base  can  be  used. 


NH4C1 


NaOH  ->  NH 
H20  +  NaCl 


f 


Properties  of  ammonia.    The 

gas   thus   Obtained    is    Colorless,     FIG.  48.  -Preparation  of  ammonia. 

and  has  a  very  pungent  characteristic  odor.  Since  am- 
monia contains  hydrogen,  you  might  expect  it  to  burn.  If 
we  try  the  experiment  of  directing  a  stream  of  the  gas  coming 
from  the  delivery  tube  against  a  Bunsen  burner  flame,  you 
will  notice  that  the  ammonia  gas  burns  as  long  as  it  is  in  the 

145 


146  CHEMISTRY   IN   THE   HOME 

Bunsen  burner  flame,  but  that  when  removed,  it  goes  out. 
That  is,  ammonia  will  burn  only  so  long  as  we  supply  it  with 
heat.  It  will  not  burn  under  ordinary  conditions. 

It  is  very  soluble  in  water.  At  50°  F.,  one  quart  of  water 
will  dissolve  670  quarts  of  the  gas.  This  solution  is  not 
merely  physical,  but  a  new  compound  is  formed,  ammonium 
hydroxide. 

NH,  +  H20  ->  NH4OH 

The  colorless  solution  has  a  sharp,  burning  taste,  and  smells 
of  ammonia.  It  has  many  names :  ammonium  hydroxide, 
ammonia  water,  aqua  ammonia,  and  spirits  of  hartshorn. 
It  is  an  unstable  compound,  heat  easily  breaking  it  up  into 
ammonia  and  water.  This  suggests  a  quick  method  of 
obtaining  ammonia  in  the  laboratory,  when  we  wish  a  little 
of  the  gas. 

NH4OH  +  heat  ->  NH3  f  +  H2O 

The  "  household  ammonia  "  that  you  buy  for  cleaning  pur- 
poses is  a  weak,  impure,  ammonium  hydroxide,  obtained  as  a 
waste  product  in  certain  manufacturing  operations.  You 
will  get  much  more  for  your  money  if  you  will  buy  a  bottle 
of  the  concentrated  aqua  ammonia,  and  dilute  it  as  you 
need  it. 

Commercial  production  of  ammonia.  Commercially, 
ammonia  is  made  by  the  destructive  distillation  of  soft 
coal.  Since  soft  coal  is  a  product  of  the  partial  decay  of 
wood  in  the  earth,  it  contains  hydrogen  and  nitrogen. 
When  it  is  heated  out  of  contact  with  the  air,  illuminating 
gas,  coal  tar,  and  ammonia  are  formed.  The  ammonia 
is  absorbed  in  water,  and  from  this  "  gas  liquor  "  the  am- 
monia of  trade  is  obtained.  Ammonia  gas  is  cooled  and 
compressed  until  it  changes  to  a  liquid,  in  which  form  it  is 


AMMONIA   AND   AMMONIUM   COMPOUNDS      147 

sold  in  iron  cylinders.  It  is  used  largely  in  the  manufacture 
of  artificial  ice  (p.  93). 

The  radical  ammonium.  If  you  compare  the  formulas 
of  sodium  and  ammonium  hydroxides,  NaOH  and  NH4OH, 
you  will  notice  that  the  group  of  atoms  NH4  takes  the  place 
of  the  sodium  atom.  This  NH4  group  we  call  a  radical,  be- 
cause in  reactions  it  tends  to  stick  together  and  act  like 
one  atom.  Since  it  takes  the  place  of  a  metal,  we  call  it  a 
metallic  radical.  Since  it  forms  the  compound  NH4OH, 
its  valence  must  be  one.  Notice  that  the .  ending  -ium  is 
given  to  metals  only,  as  sodium,  potassium,  and  aluminium. 
Since  NH4  plays  the  part  of  a  metal,  it  is  called  ammonium. 
Be  careful  not  to  confuse  the  gas  ammonia  with  the  radical 
ammonium.  Radicals  never  occur  free,  but  exist  only  in 
compounds. 

Ammonium  salts.  Ammonium  forms  many  salts,  as 
ammonium  sulphate,  ammonium  chloride,  and  ammonium 
nitrate.  Two  ammonium  salts  are  much  used  in  the  home. 

Ammonium  chloride,  formed  by  neutralizing  ammonium 
hydroxide  with  hydrochloric  acid,  is  a  white,  crystalline 
body,  often  called  sal  ammoniac. 

NH4OH  +  HC1  -+  NH4C1  +  H2O 

It  is  the  material  used  in  the  common  wet  battery  used  to 
ring  bells.  The  next  time  your  door  bell  does  not  ring,  go 
to  the  cellar  and  examine  the  battery.  Perhaps  the  water 
has  evaporated,  in  which  case  fill  it  up,  and  in  a  few  hours 
it  will  be  in  order  again.  If  this  is  not  the  cause  of  the  trou- 
ble, disconnect  the  battery,  and  wash  out  the  old  solution. 
Buy  five  cents'  worth  of  sal  ammoniac,  dissolve  it  in  a  little 
water,  and  place  the  solution  in  the  jar.  Fill  it  up  with 
water,  again  connect  the  wires,  and  probably  the  bell  will 

WEED'  CHEMISTRY  — 10 


148  CHEMISTRY   IN   THE    HOME 

ring  again  as  before.  Ammonium  chloride  is  one  of  the 
substances  used  in  the  dry  cell,  which  is  now  largely  replac- 
ing the  wet  battery.  Ammonium  chloride  is  also  used  in 
soldering. 

Ammonium  carbonate,  or  sal  volatile,  is  prepared  by 
heating  a  mixture  of  calcium  carbonate  and  ammonium  chlo- 
ride. It  is  a  white,  fibrous  mass,  that  slowly  decomposes  in 
the  air,  giving  off  ammonia.  It  is  this  property  that  makes  it 
useful  to  you.  A  lump  placed  in  a  bottle,  with  the  addition 
of  a  little  lavender  water,  forms  the  smelling  salts  that  are 
so  refreshing. 

Ammonium  salts  resemble  those  of  sodium.  They  are 
easily  identified  because  they  all  give  off  ammonia  when 
treated  with  a  base,  and  they  all  sublime  when  heated. 

SUMMARY 

Preparation  of  ammonia.  Ammonia  is  prepared  by  the  action  of  a 
base  on  an  ammonium  salt,  or  by  heating  ammonium  hydroxide. 

Properties  of  ammonia.  Ammonia,  is  a  colorless  gas,  very  soluble 
in  water  forming  a  base,  burns  only  when  supplied  with  addi- 
tional heat,  and  has  a  characteristic  odor. 

Ammonium  is  a  metallic  radical  and  forms  salts  like  those  of  sodium. 

Ammonium  chloride  is  used  in  bell  batteries  and  in  soldering. 

Ammonium  carbonate  is  used  in  smelling  salts. 

Exercises 

1.  Is  it  economical  to  buy  "  household  ammonia  "? 

2.  Can  you  prepare  smelling  salts  at  home? 

3.  Name  NH4NO3,  (NH)2  S04. 

4.  Some  soaps  are  said  to  contain  ammonia.     From  what  you 
know  of  ammonia,  do  you  think  they  can  contain  enough  to  be  of 
any  use?     Explain. 

5.  Why  do  decaying  leaves  smell  of  ammonia  ? 

6.  How  can  you  tell  which  of  two  samples  of  ammonia  water  is 
the  stronger? 


CHAPTER  XV 

METALS 

Metals  and  nonmetals  distinguished.  When  we  attempt 
to  define  the  word  metal,  we  encounter  certain  difficulties. 
You  would  perhaps  say  that  a  metal  is  a  hard,  heavy  body, 
having  a  metallic  luster.  But  sodium,  which  chemically  is 
an  exceedingly  good  metal,  is  soft,  lighter  than  water,  and, 
as  usually  seen,  has  no  luster.  Iron  pyrites,  or  fool's  gold, 
one  of  the  sulphides  of  iron,  is  hard,  heavy,  and  has  a  strongly 
marked  metallic  luster,  but  it  is  not  a  metal.  You  might 
add  to  your  list  of  metallic  properties,  that  metals  conduct 
heat  and  electricity  well.  This  is  true,  but  some  nonmetals 
conduct  heat  and  electricity  as  well  as  some  metals.  These 
physical  properties  are  not  a  satisfactory  basis  for  an  exact 
definition  of  the  word  metal. 

Chemically,  metals  are  easier  to  define.  When  oxygen 
was  studied,  you  learned  that  sodium  oxide,  when  dissolved 
in  water,  formed  sodium  hydroxide,  and  gave  a  solution 
that  turned  red  litmus  paper  blue.  Sodium  hydroxide  is 
a  base.  Magnesium,  potassium,  calcium,  and  other  metals 
act  in  the  same  way,  that  is,  their  hydroxides  are  bases. 
We  also  know  that  all  of  these  metals  form  salts.  We  may, 
then,  from  a  chemical  standpoint,  easily  give  a  satisfactory 
definition.  A  metal  is  a  substance  whose  hydroxide  is  a 
base,  and  which  forms  the  positive  part  of  a  salt.  We  may 
add  to  this  certain  physical  properties.  Metals  are  solids, 

149 


150  CHEMISTRY   IN   THE   HOME 

with  the  exception  of  mercury.  They  can  all  be  obtained 
in  a  crystalline  form,  conduct  heat  and  electricity  well, 
and  are  generally  malleable. 

It  is  not  always  possible  to  draw  a  sharp  line  between 
metals  and  nonmetals.  Some  elements,  as  arsenic,  have 
properties  intermediate  in  their  nature  between  those  of 
metals  and  nonmetals.  If  we  are  thinking  of  arsenic  as 
compared  to  chlorine,  it  is  a  metal.  But,  compared  to 
sodium,  it  is  a  nonmetal.  Thus  we  have  arsenic  chloride, 
AsCl3,  but  sodium  arsenate,  Na3AsO4. 

The  general  methods  of  obtaining  metals.  With  the 
exception  of  a  few  metals,  as  copper,  gold,  and  silver,  metals 
do  not  occur  in  nature  in  the  metallic  form.  The  most 
important  of  their  naturally  occurring  compounds  are  the 
oxides,  carbonates,  and  silicates.  Metallurgy  is  the  art 
of  extracting  the  metal  from  these  compounds  or  ores. 
There  are  two  main  methods:  reducing  the  metal  from  its 
compounds  by  the  use  of  carbon,  and  by  electrolysis.  As 
the  electric  current  has  been  available  only  within  recent 
years,  you  may  be  sure  that  any  metal  known  to  the  ancients, 
as  iron,  is  either  found  free  in  nature,  or  is  obtained  by  re- 
duction with  carbon;  while  such  metals  as  aluminium  and 
sodium,  that  have  only  recently  come  into  use,  cannot  be 
obtained  by  reduction  with  carbon,  but  are  obtained  by 
electrolysis  or  by  some  difficult  chemical  process. 

Metallurgy  of  iron.  The  metallurgy  of  iron  illustrates 
the  method  of  obtaining  metals  by  reduction  with  carbon. 
Iron  compounds  occur  everywhere  in  soil.  The  red  color 
of  ordinary  brick  is  due  to  the  presence  of  small  amounts 
of  iron  oxide,  and  common  red  roofing  paint  is  largely  natural 
iron  oxide.  In  the  Lake  Superior  region  of  the  United  States, 
large  deposits  of  iron  oxide  occur  as  the  mineral  hematite, 


METALS 


151 


Fe2O3.  This  ore  is  mined  and  carried  to  a  blast  furnace, 
where  it  is  heated  with  carbon,  and  so  reduced  to  metallic 
iron.  The  carbon  necessary  is  usually  used  in  the  form  of 
coke,  produced  by  heating  soft  coal  without  access  of  air. 
If  the  iron  ore  contains  nothing  but  iron  oxide,  and  the  coke 
nothing  but  carbon,  all  that  is  necessary  is  to  heat  the  two 
together.  The  coke  combines  with  the  oxygen  of  the  iron 
oxide,  and  pure  iron  is  obtained. 

2  Fe2O3  +  3  C  ->  4  Fe  +  3  CO2 

However,  both  ore  and  coke  contain  certain  impurities,  and  so 
it  is  necessary  to  add  something  that  will  combine  with  these 
impurities  and  produce  a  fusible  mass  called  a  slag.  This 


Ore 

Fe2O3 

Fuel 
Carbon 

Air  Blast 
Oxygen 

Flux 
SiO2 
CaCO3 

> 

Blast  Furnace 
Gas 

FIG.  49.  —  Diagram  showing  raw  materials  and  products 
in  manufacture  of  cast  iron. 

third  addition  is  called  a  flux.  If  these  impurities  consist 
of  metallic  oxides  or  carbonates,  silica  is  used  as  a  flux. 
In  the  heat  of  the  furnace,  all  these  combine  to  form  a  sili- 
cate, a  fusible  glass,  and  this,  being  lighter  than  the  metal, 
floats  upon  the  molten  iron  in  the  lower  part  of  the  furnace. 


152 


CHEMISTRY   IN   THE    HOME 


The  blast  furnace.  To  obtain  iron  from  the  ore,  we 
must  have  a  blast  furnace  in  which  to  heat  it.  This  con- 
sists of  a  huge  brickwork, 
one  hundred  or  more  feet 
in  height,  and  twenty  feet 
through  at  its  widest  part. 
In  shape,  it  is  something 
like  two  cones  put  together 
base  to  base.  Near  the 
bottom  there  are  two  small 
openings  at  different  levels, 
through  which  the  iron  and 
the  slag  may  be  drawn  off. 
While  the  furnace  is  in 
operation,  these  are  kept 
closed  by  plugs  of  fire  clay. 
There  are  also  openings 
through  which  air  is  blown 
into  the  furnace.  The  top 
of  the  furnace  is  closed  in 
such  a  way  that  materials 
may  be  introduced  through 
what  is  really  a  trapdoor. 

The  ore,  fuel,  and  flux  are 
put  in  at  the  top,  and  sink 
slowly  through  the  furnace. 
At  the  bottom,  hot  air  is 
blown  in.  As  the  coke 
burns,  it  forms  carbon  mon- 


on  Conve/or. 

B.Upper 

flopper. 

C.  Upper  Be//. 

D.  Lower 

flopper. 
E.Lowerdell. 


FIG.  50.  —  A  blast  furnace. 


oxide,  and  this  acts  upon  the  iron  oxide,  reducing  it,  and 
forming  metallic  iron.  At  the  same  time  the  impurities  and 
flux  combine  to  form  the  fusible  glass  or  slag.  The  molten 


METALS  153 

iron  and  the  slag  drop  to  the  bottom  of  the  furnace,  where 
they  separate,  the  slag  floating  on  the  top  of  the  iron.  When 
a  sufficient  quantity  has  accumulated,  the  plugs  of  fire  clay 
closing  the  openings  are  knocked  out,  and  then  the  slag  and 
iron  flow  out.  The  iron  is  made  to  flow  into  shallow  troughs, 
made  in  a  bed  of  sand.  Here  it  solidifies  in  the  form  of 
bars  called  "  pigs,"  hence  the  name,  pig  iron.  The  slag 
is  sometimes  used  in  making  cement,  or  as  ballast  for  a  rail- 
road track. 

The  pig  iron  or  cast  iron  produced  in  this  way  is  very 
impure,  containing  perhaps  3  %  of  carbon  and  3  %  of 
silicon,  as  well  as  small  amounts  of  sulphur,  phosphorus, 
and  manganese.  It  gets  its  name  of  cast  iron  from  an 
extensive  use  that  is  made  of  it.  Since  it  is  both  cheap 
and  fusible,  it  is  used  extensively  in  the  form  of  cast- 
ings for  iron  fences,  radiators,  posts,  and  numerous  other 
appliances  in  everyday  use.  It  is  brittle,  and  so  cannot 
be  used  where  a  bending  strain  or  a  sudden  blow  has  to  be 
resisted.  It  is,  however,  strong  in  resisting  compression. 
It  is  made  in  very  large  amounts,  as  will  be  seen  from  the 
table  below. 

PRODUCTION  OF  PIG  IRON  OF  WORLD  FOR  1912 

LONG  TONS  LONG  TONS 

United  States  .  .  .  29,726,937  France  .....  4,870,913 
Germany  ....  17,586,521  Other  Countries  .  .  11,542,599 
Great  Britain  .  .  .  8,839,124  Total 72,566,094 

Making  wrought  iron.  Cast  iron  is  the  starting  point 
for  the  manufacture  of  both  wrought  iron  and  steel.  To 
make  wrought  iron,  the  cast  iron  is  placed  in  a  reverberatory 
furnace.  This  consists  of  a  horizontal  bed,  with  a  low  roof 
curved  so  that  the  heat  and  flames  are  deflected  down  upon 
whatever  material  is  placed  on  the  bed.  The  bed  of  the  re- 


154 


CHEMISTRY   IN   THE   HOME 


verberatory,  or  puddling  furnace  as  it  is  called,  is  first  lined 
with  iron  oxide,  the  cast  iron  is  then  placed  on  it,  the  fire 
started,  and  the  melting  begins.  The  melted  iron  is  stirred, 
and  carbon,  silicon,  and  other  impurities  are  slowly  burned 
out.  Almost  pure  iron  results.  Pure  iron  is  much  less 

fusible  than  the  im- 
pure cast  iron,  so 
that,  as  the  end  of 
the  operation  ap- 
proaches, the  mass 
becomes  pasty.  This 


pasty  mass  is  then 
squeezed  between 
rolls  so  as  to  press 
out  the  slag. 


FIG.  51.  —  Reverberatory  furnace. 


To  make  the  wrought  iron  uniform  in  composition,  it  is 
rolled  into  bars,  these  are  piled  one  on  another,  and,  after 
heating,  again  rolled  into  bars.  The  wrought  iron  thus 
produced  is  a  tough,  fibrous  material,  which  can  be  welded.1 
It  is  used  where  it  is  necessary  to  make  iron  parts  by  forging.2 
Its  freedom  from  carbon  is  believed  to  be  the  reason  why 
wrought  iron  resists  corrosion  so  successfully.  It  would 
be  used  more  extensively,  were  it  not  for  its  comparatively 
high  cost.  Its  cost  is  high  because  it  is  made  in  small 
batches  of  perhaps  600  pounds,  hand  labor  is  required,  and 
the  time  required  to  make  each  batch  is  considerable. 

1  If  two  pieces  of  wrought  iron  are  heated  red  hot,  placed  one 
over  the  other,  and  then  hammered,  they  stick  together,  and  form 
one  piece.     The  operation  is  called  welding.     It  is  in  this  way  that 
the  blacksmith  makes  a  wagon  tire. 

2  If  a  piece  of  wrought  iron  is  heated  red  hot,  it  becomes  soft,  and 
can  be  hammered  into  any  shape  that  the  blacksmith  wishes  to 
make.     This  is  called  forging. 


METALS 


155 


Making  crucible  steel.  From  this  wrought  iron  the  best 
grade  of  steel  is  made.  Small  pieces  of  wrought  iron,  about 
90  pounds,  are  placed  in  a  crucible  together  with  carbon  in 
the  form  of  charcoal.  When  this  crucible  is  heated  in  a  fur- 
nace, the  iron  absorbs  the  carbon,  melts,  and  is  changed  into 
crucible  steel  (Fig.  52).  This  is  the  material  from  which 
high-grade  knives,  springs,  and  things  that  must  be  both 


Courtesy  of  Crucible  Steel  Company  of  America. 
FIG.  52. —  Crucible  steel  furnace. 

hard  and  springy  are  made.     It  is  made  in  small  quantities 
but  it  is  the  best  grade  of  steel. 

Bessemer  and  open-hearth  steel.  An  easier  way  to  burn 
out  the  impurities  from  cast  iron  is  to  blow  air  through  molten 
pig  iron.  .This  product  is  called  Bessemer  steel.  Ten  to 
twenty  tons  of  molten  cast  iron  are  placed  in  a  large  vessel, 
called  a  converter,  lined  with  an  infusible  fire  clay.  The 
bottom  of  this  converter  has  many  holes,  each  of  which  is 


156 


CHEMISTRY   IN   THE   HOME 


about  the  size  of  a  lead  pencil  (Fig.  53).  Through  these 
holes  air  is  blown,  and  in  about  twelve  minutes  the  impuri- 
ties are  burned  out.  After  the  carbon  has  been  burned  out, 
an  alloy  of  iron  containing  a  definite  amount  of  carbon  and 

manganese  is  added. 
This  produces  a  steel 
with  a  known  amount 
of  carbon. 

In  still  another 
method,  called  the 
open-hearth  process, 
pig  iron  is  melted, 
together  with  scrap 
iron,  in  a  large,  low, 
square  room,  heated 
by  burning  gas  (Fig. 
54).  The  furnace 
hearth  is  lined  with 
compounds  of  silica 
or  with  dolomite, 
depending  upon  the 
kind  of  iron  used.  Here  the  impurities  are  slowly  burned 
out.  When  the  carbon  has  been  reduced  sufficiently,  the 
process  is  stopped  and  open-hearth  steel  results. 

How  steel  is  hardened.  When  steel  is  heated  and  then  sud- 
denly cooled  by  plunging  it  into  water,  it  becomes  very  hard. 
This  is  the  process  used  to  harden  needles  and  knife  blades. 
This  hardening  process  leaves  the  steel  so  brittle,  that 
it  breaks  like  glass.  If,  however,  it  is  slightly  reheated, 
it  becomes  softer  and  less  brittle.  By  regulating  the 
temperature  to  which  we  reheat  the  steel,  we  can  give  it 
any  desired  hardness.  The  higher  the  temperature  to  which 


FIG.  53.  —  Bessemer  converter. 


METALS 


157 


it  is  heated,  the  softer  the  steel  becomes.  This  is  called 
"  drawing  the  temper." 

Iron  and  steel  contrasted.  Wrought  iron  is  the  purest 
form  of  iron,  and  cast  or  pig  iron  the  most  impure.  Steel 
is  intermediate  in  composition. 

The  iron  and  steel  industry  is  a  good  example  of  the  large 
size  of  some  of  our  modern  industries.  Furnaces  in  many  cases 


n~wfi///// 
7/^/M, 


FIG.  54. —  Open-hearth    furnace.      A,  B,  Air  and    gas  heated  by  passing 

over  hot  bricks.      C,  Steel  in  process  of  making.      D,  Hearth' lining. 

E,  F,  Bricks  heated  by  gaseous  products.  These  are  later  made  inlets 
to  warm  the  entering  air  and  gas. 

have  a  production  of  six  hundred  tons  of  pig  iron  a  day.  To 
produce  a  ton  of  pig  iron  requires  about  two  tons  of  ore,  one 
half  a  ton  of  flux,  one  ton  of  carbon,  and  four  tons  of  blast. 
About  one  half  ton  of  slag  and  six  tons  of  waste  gases  are 
formed. 

How  iron  is  protected  from  rust.  Pure  iron  is  a  soft, 
ductile,  white  metal.  It  readily  dissolves  in  acids.  The 
purest  form  of  iron  that  you  are  familiar  with  is  probably 


158  CHEMISTRY   IN   THE   HOME 

the  thin  wire  that  florists  use  in  wiring  flowers.  In  damp  air, 
iron  rusts  easily,  and  for  that  reason  iron  kitchen  utensils  are 
often  protected  by  coating  the  iron  with  some  metal,  as  nickel, 
zinc,  or  tin,  that  does  not  readily  oxidize.  Iron  buildings 
and  bridges  are  protected  from  corrosion  by  painting  them. 

Galvanized  iron.  Galvanized  iron  is  iron  coated  with 
zinc  to  prevent  it  from  rusting.  To  make  a  galvanized- 
iron  pail,  a  sheet-iron  pail  is  dipped  into  acid  to  clean  it, 
and  is  then  washed  and  dried.  It  is  then  dipped  into  melted 
zinc.  This  forms  a  coating  over  the  iron,  and,  since  zinc  does 
not  corrode  in  the  air,  the  pail  is  made  much  more  durable. 

In  using  galvanized  articles,  care  should  be  taken  not  to 
bend  them,  as  this  may  crack  the  coating  of  zinc.  The 
iron  is  then  exposed  to  the  air,  rusts,  and  soon  the  pail  has 
a  hole  in  .it. 

Tin  ware.  Tin  is  another  of  the  metals  used  extensively 
in  the  home.  The  tin  pans  that  you  use  are  really  not  tin, 
however,  but  sheet  iron  coated  with  tin.  The  sheet  iron 
is  first  carefully  cleaned,  and  then  dipped  into  a  bath  of 
molten  tin.  The  plates  are  then  passed  between  steel  rollers, 
set  close  together,  so  as  to  squeeze  off  as  much  of  the  tin  as 
possible.  This  leaves  a  thin  coat  of  tin  covering  the  iron. 
As  tin  does  not  corrode  in  the  air,  it  serves  to  protect  the 
iron  underneath,  while  the  iron  gives  strength  and  stiffness 
to  the  utensil. 

Tin  and  lead  alloy  readily,  as  is  seen  in  solder.  The  tin 
foil  that  is  usually  used  is  really  made  from  an  alloy  of  tin 
and  lead. 

Nickel  plate.  Other  metals  are  used  to  cover  iron  and 
protect  it.  Nickel  is  often  used,  as  in  the  handles  of  stove 
doors.  It  is  plated  upon  the  iron  by  using  a  bath  of  nickel 
ammonium  sulphate,  making  the  object  to  be  plated  the 


METALS  159 

cathode,1  and  using  a  plate  of  nickel  for  the  anode.  On 
passing  an  electric  current  through  the  solution,  the  nickel 
is  taken  from  the  anode  and  deposited  on  the  iron  as  a  thin 
protective  coat. 

Manufacture  of  aluminium.  The  production  of  alu- 
minium is  typical  of  the  methods  used  for  obtaining  metals 
by  electrolysis.  The  starting  point  is  the  mineral  bauxite, 
which  is  the  hydroxide  of  aluminium.  This,  when  heated, 
is  changed  into  the  oxide.  As  the  electric  current  will  not 
flow  through  the  solid  oxide,  it  is  necessary  to  dissolve  it. 
Aluminium  oxide  is  insoluble  in  water,  but  readily  dissolves 
in  the  mineral  cryolite.2 

A  box  lined  with  carbon  serves  as  the  cathode,  and  large 
carbon  rods  as  the  anode  (Fig.  55).  In  this  box  the  fused 
cryolite,  containing  the  aluminium  oxide,  is  placed.  The 

current   in  passing      ^^^^^^^^^..^^^^  

through  the  solution 
decomposes  it,  and 
aluminium  is  set  free 
at  the  cathode.  Oxy- 
gen is  set  free  at  the 
anode,  combines  with 

.  FIG.  55.  —  Manufacture  of  aluminium. 

the   carbon,   and   es- 
capes as  carbon  dioxide.     The  temperature  of  the  bath  is  so 
high  that  the  aluminium  melts  and  drops  to  the  bottom  of 
the  box,  whence  it  is  drawn  from  time  to  time. 
Properties    of   aluminium.     Metallic    aluminium    has   a 

1  The  plate  by  which  the  current  enters  is  the  anode  and  the  one 
by  which  it  leaves  is  the  cathode. 

2  Cryolite  is  a  white  mineral  found  in  Greenland.     It  is  remark- 
able because  a  splinter  of  it  will  melt  in  the  flame  of  a  candle.     It 
is  sodium  aluminium  fluoride,  Na3AlF«. 


160  CHEMISTRY   IN   THE   HOME 

bluish  white  color,  is  light,  having  a  specific  gravity  of  only 
2.6,  and  is  quite  soft.  It  is  ductile,  malleable,  and  tenacious. 
It  is  used  as  a  conductor  of  electricity,  for  cups,  saucepans, 
etc.,  and  wherever  strength  and  lightness  are  required. 
The  metal  keeps  bright  when  exposed  to  the  air.  It  oxidizes 
quite  easily,  but  the  thin  film  of  oxide  that  forms  is  trans- 
parent and  so  does  not  show.  This  film  protects  the  metal 
from  any  further  action  of  the  air. 

Aluminium.  It  is  satisfactory  for  cooking  utensils.  It  is 
readily  kept  clean,  and,  as  heat  is  easily  transmitted  through 
the  thin  metal,  liquids  are  quickly  heated  in  it.  It  has 
a  decided  advantage  over  enamel  or  agate  ware  in  that 
it  does  not  chip,  wears  much  longer,  and  does  not  act 
as  a  heat  insulator  as  does  agate  ware.  It  must  be  cleaned 
with  a  neutral  substance,  as  strong  acids  and  alkalies  turn 
it  black.  It  is  not  suitable  for  frying  or  pastry,  as  the  metal 
heats  so  quickly  that  things  stick  and  burn.  It  is  ideal 
for  teakettles  and  double  boilers. 

Aluminium  is  used  in  many  alloys,  as  in  aluminium  bronze, 
an  alloy  of  copper  and  aluminium  having  the  color  of  gold 
and  the  strength  of  steel. 

Aluminium  oxidizes  so  easily  that  it  is  used  in  flashlights. 
The  powdered  metal  is  mixed  with  an  oxidizing  agent,  when 
it  burns  with  an  exceedingly  bright  and  actinic  light.1  As 
these  flashlights  are  really  a  variety  of  explosive,  they 
should  be  handled  with  care. 

The  powdered  metal  is  also  used  as  a  paint.  Celluloid 
is  soluble  in  amyl  acetate,  and  this  solution,  when  mixed 

1  Blue  light  aids  chemical  action  much  more  than  red  light.  It 
is  for  this  reason  that  we  use  red  lamps  in  a  photographic  dark 
room.  We  say  that  these  blue  rays  of  light  are  very  actinic.  An 
actinic  light  is  one  rich  in  the  blue  and  violet  rays  that  cause  chemi- 
cal action. 


METALS  161 

with  aluminium  powder,  makes  a  good  metallic  paint  for 
steam  pipes  and  radiators. 

Lead  and  its  uses.  Water  pipes  are  sometimes  made  of 
lead.  This  soft,  white  metal  melts  at  a  low  temperature, 
is  easily  bent,  and  is  an  ideal  material  for  pipes,  as  it  does 
not  readily  corrode  in  the  air.  All  natural  \vaters  act 
somewhat  on  lead  pipes,  and,  in  some  cases,  the  corrosion  is 
so  marked  that  it  is  not  safe  to  use  them.  Lead  hydroxide 
is  formed,  and  the  carbon  dioxide  present  converts  this 
into  a  carbonate.  Lead  salts  are  poisonous,  and  their 
action  is  cumulative.  That  is,  lead  is  not  eliminated  from 
the  body,  and  slowly  accumulates  until  enough  is  present 
to  produce  illness.  Painters  often  suffer  from  lead  poisoning, 
as  common  paint  contains  white  lead  or  basic  lead  carbonate. 

Gold  and  its  uses.  Gold  is  a  yellow  metal.  It  is  about 
as  soft  as  lead,  and  is  the  most  malleable  of  all  the  metals. 
By  first  rolling  gold  until  it  is  thin,  and  then  placing  the 
thin  sheets  between  gold  beaters'  skin  and  hammering,  it 
can  be  beaten  out  so  thin  that  250,000  sheets  would  be  only 
one  inch  thick.  Dutch  metal  leaf,  which  is  thin  brass,  is 
an  imitation  of  gold  leaf.  The  two  can  easily  be  distinguished, 
for  the  gold  transmits  a  green  light,  while  the  Dutch  metal 
is  opaque. 

Gold*  does  not  tarnish  in  air.  For  this  reason,  and  be- 
cause of  its  high  cost,  its  beautiful  color,  and  luster,  it  is 
used  in  jewelry.  The  pure  metal  would  be  too  soft  to  use, 
as  it  would  wear  out  very  quickly.  It  is  therefore  alloyed 
with  some  harder  metal.  Silver  and  copper  are  used.  Silver 
gives  the  gold  a  pale  color,  while  copper  makes  it  red.  Other 
metals  vary  the  color,  arsenic,  for  instance,  making  it  green. 

The  purity  of  gold  is  expressed  in  carats.  Pure  gold  is 
24  carats  fine.  A  suitable  fineness  for  general  use  is  14 


162 


CHEMISTRY   IN   THE   HOME 


carat,  that  is,  fourteen  pounds  of  gold  to  ten  pounds  of  copper. 
This  alloy  is  hard,  of  a  good  color,  and  is  not  too  expensive. 
Gold  coins  contain  nine  parts  of  gold  to  one  part  of  copper. 
Articles  should  not  be  marked  "  solid  gold."  Suppose 
a  pin  is  really  eight  carats  fine.  This  means  that  it  will 
contain  two  pounds  of  copper  to  one  pound  of  gold,  but, 
since  the  specific  gravity  of  gold  is  more  than  twice  that  of 
copper,  it  means  that,  by  volume,  there  will  be  only  one 
sixth  gold.  If  this  pin  is  marked  "  solid  gold,"  the  pur- 
chaser imagines  that  he  is  getting  pure  gold,  while  in  reality 
it  is  far  from  pure.  It  is  much  better  to  mark  the  exact 
carat,  then  the  buyer  knows  what  he  is  purchasing. 

Silver  and  its  uses.  Silver  is  much  harder  than  gold. 
The  oxygen  of  pure  air  does  not  affect  it,  but  air,  especially 
the  air  of  cities,  contains  hydrogen  sulphide.  This  changes 
the  silver  to  silver  sulphide,  and  thus  blackens  it.  The 
"  oxidized  silver "  of  the  jeweler  is  really  silver  covered 

with  black  silver  sulphide.  To 
keep  silver  bright,  it  must  be  kept 
from  this  gas. 

Sterling  silver  is  silver  that  con- 
tains, in  each  1000  pounds,  925 
pounds  of  silver.  The  remaining 
75  pounds  is  metal  used  to  alloy 
it,  usually  copper.  Coin  silver 
contains  90  %  silver  and  10  % 
copper. 

Large  silver  teapots  and  other 
vessels  are  made  by  plating  silver 
upon  a  white  metal  base.  This  is 
an  alloy  of  lead  and  tin  called  pewter.  The  thickness  of  the 
coating  is  denoted  by  the  name,  as  "  triple  plate/'  This  does 


FIG.  56.  —  Silver  plating. 


METALS 


163 


not  mean  that  the  vessel  has  been  plated  three  times,  but  that 
three  times  the  standard  amount  of  silver  has  been  deposited 
upon  it.  Silver  is  plated  in  the  same  way  as  nickel,  using  a 
plate  of  silver  for  the  anode,  and  the  article  to  be  plated  as 
the  cathode  (Fig.  56).  The  bath  is  usually  silver  cyanide, 
dissolved  in  potassium  cyanide. 

Copper.  Pure  copper  is  a  rather  soft,  malleable,  duc- 
tile, reddish  metal,  that  is  a  very  good  conductor  of  both 
heat  and  electricity.  It  is  used  in  large  quantities  in  elec- 
tric light  and  telephone  wires,  and  in  other  electrical  work. 
Its  high  thermal  conductivity  also  makes  it  suitable  for 
kitchen  pots  and  pans.  It  corrodes  easily,  and  as  copper 
salts  are  poisonous,  care  must  be  used  to  keep  kitchen 
utensils  bright.  It  is  easily  cleaned,  either  with  an  abrasive, 
or  by  oxalic  acid  or  ammonia,  which  dissolves  the  tarnish. 

Use  of  alloys  in  sprinkler  heads.  Many  of  the  metals 
when  melted  mix  with  each  other  to  form  solutions  known 
as  alloys.  An  alloy  is  usually  more  fusible  than  the  met- 
als that  compose  it.  Thus 
Wood's  metal  is  made  up 
of  tin  and  cadmium,  each 
one  part,  lead  two  parts, 
and  bismuth  four  parts.  It 
melts  at  165°  F.,  which  is 
lower  than  the  melting  point 
of  any  of  its  constituents. 
This  low  melting  point  of 
the  alloy  is  made  use  of  in 
sprinkler  heads  (Fig.  57). 
Many  factories  and  stores 
are  now  protected  against 
fire  by  covering  the  ceilings 

WEED   CHEMISTRY 11 


FIG.  57.  —  A  sprinkler  head. 


164  CHEMISTRY   IN   THE   HOME 

with  a  network  of  pipes  having  at  short  intervals  openings 
closed  normally  with  a  plug  of  Wood's  metal.  Should  a  fire 
occur  when  the  building  is  unguarded,  the  heat  will  melt 
the  easily  fusible  metal.  Water  will  then  flow  through  the 
pipes,  and,  falling  upon  the  fire,  extinguish  it.  Thus  the 
damage  is  small.  The  system  is  usually  so  arranged  that 
the  melting  of  a  plug  not  only  turns  on  the  water,  but  rings 
an  alarm  in  the  watchman's  room. 

Some  household  alloys.  Some  alloys  are  of  particular 
interest  in  the  household.  Brass  is  an  alloy  of  copper  and 
zinc.  Solder  an  alloy  of  lead  and  tin.  The  larger  the  per- 
centage of  lead,  the  more  easily  the  solder  melts,  but  also 
the  weaker  it  is.  The  small  strips  of  "  soft  solder  "  sold 
to  mend  tin  kettles  are  of  small  value,  as  they  contain 
so  much  lead  that  they  have  little  strength.  Bronze  is  an 
alloy  of  copper  and  tin.  It  usually  also  contains  some  zinc. 

Amalgams.  The  alloys  obtained  by  dissolving  metals 
in  mercury  are  given  a  special  name,  amalgams.  Teeth 
are  often  filled  with  an  amalgam.  Gold  is  sometimes  ex- 
tracted from  its  ores  by  grinding  the  powdered  wet  ore 
with  mercury.  The  mercury  dissolves  the  gold,  forming 
gold  amalgam.  On  heating  this,  the  mercury  volatilizes, 
leaving  the  gold. 

SUMMARY 

A  metal  is  a  substance  whose  hydroxide  is  a  base. 

Iron  is  obtained  by  heating  iron  oxide,  coke,  and  a  flux  in  a  blast 

furnace. 

Galvanized  iron  is  iron  coated  with  zinc. 
Tin  plate  is  iron  coated  with  tin. 
Nickel  is  plated  on  iron,  to  protect  the  iron  from  rusting,  as  well  as 

to  give  a  good  appearance. 
Aluminium  is  obtained  by  electrolyzing  a  solution  of  aluminium 

oxide  in  fused  cryolite. 


METALS  165 

Lead  is  poisonous,  and  care  must  be  taken  in  using  lead  pipes. 
Gold  is  the  most  malleable  metal.     Pure  gold  is  24  carats  fine. 
Coin  silver  is  90%  silver. 
Sterling  silver  is  92.5%  silver. 

Copper  is  a  soft,  malleable  metal,  used  for  electrical  conductors  and 
kitchen  utensils.     Its  salts  are  poisonous. 

Exercises 

1.  How  could  you  harden  a  knife  blade  that  is  too  soft? 

2.  Why  is  the  soil  in  many  localities  red? 

3.  Why  does  a  spot  of  rust  often  form  on  a  tin  pan? 

4.  Why  are  galvanized  pails  used  instead  of  zinc  pails? 

5.  Why  is  an  aluminium  teakettle  better  than  an  iron  one? 

6.  Would  you  rather  have  a  22-carat,  or  a  14-carat  gold  ring? 
Why? 

7.  Aluminium  is  worth  more  per  pound  than  brass,  but  alumin- 
ium rod  costs  less  per  foot  than  brass  rod  of  the  same  size.     Why? 

8.  How  can  you  distinguish  imitation  gold  leaf  from  the  genuine  ? 

9.  In  putting  away  your  silver  for  the  summer,  how  .should 
you  pack  it,  and  why  ? 

10.  Why  let  the  water  run  before  using  any  for  coffee  or  cereal, 
if  you  are  preparing  breakfast  for  the  family  ? 

11.  Why  should  painters  be  especially  careful  to  wash  their 
hands  before  eating? 

12.  How  can  tin  foil  be  sold  for  30  cents  a  pound,  while  tin  is 
worth  50  cents  a  pound  ? 


CHAPTER  XVI 
PHOTOGRAPHY 

Effect  of  light  on  substances.  We  see  in  our  daily  life 
many  instances  of  the  effects  that  light  and  air  have  upon 
various  materials.  The  newspaper  that  to-day  is  white, 
will  in  the  course  of  a  few  weeks  turn  to  a  yellow,  and,  in  a 
few  years,  to  a  dull  brown.  The  delicate  colors  of  ribbons 
quickly  fade  in  the  hot  sunlight  of  summer.  Carpets  fade 
in  the  sunlight,  so  that  some  too  careful  housewives  pull 
down  the  shades  to  exclude  the  sun,  and  so  deprive  them- 
selves of  necessary  light. 

It  is  a  simple  matter  to  use  these  facts  to  obtain  a  photo- 
graph. If  a  leaf  is  laid  upon  a  piece  of  blue  wrapping  paper, 
which  is  colored  with  a  fugitive  dye,  and  the  paper  then 
exposed  to  the  light,  the  color  will  bleach  except  where 
the  leaf  protects  it  from  the  action  of  the  light,  and  so  we 
shall  obtain  a  picture  of  the  leaf. 

The  difficulty  comes  in  preserving  the  picture  thus  ob- 
tained. In  time,  all  of  the  blue  dye  will  fade,  and  the  pic- 
ture disappear.  Then,  too,  such  pictures  would  be  unsatis- 
factory because  too  long  a  time  is  required  to  produce  them, 
and  because  the  half  tones  are  deficient. 

Effect  of  light  on  silver  compounds.  The  ordinary  photo- 
graph depends  upon  the  sensitiveness  of  silver  salts  to  the 
action  of  light.  When  silver  is  dissolved  in  nitric  acid,  silver 
nitrate  is  obtained.  This,  when  crystallized,  is  a  white, 

166 


PHOTOGRAPHY  167 

heavy  solid,  AgNOs.  By  careful  heating  it  can  be  melted 
without  decomposition,  and  cast  into  sticks.  It  is  then 
called  lunar  caustic,  and  is  used  to  burn  away  growths  on 
the  body,  as  it  destroys  flesh  when  brought  in  contact  with  it. 

If  you  will  examine  the  bottle  in  which  the  laboratory 
solution  of  silver  nitrate  is  kept,  you  will  notice  that  where 
the  solution  of  silver  has  trickled  down  the  outside  of  the 
bottle,  it  has  left  black  streaks.  The  deposit  is  really  me- 
tallic silver,  but  because  it  is  so  finely  divided,  it  looks  black, 
and  you  do  not  recognize  it  as  silver. 

Advantage  is  taken  of  this  fact  to  make  an  indelible  ink. 
If  a  solution  of  silver  nitrate  is  mixed  with  a  little  gum,  and 
then  used  as  an  ink  to  mark  cloth,  the  marks  will  at  first 
be  colorless,  but,  on  exposure  to  light,  they  gradually  turn 
black,  and  an  indelible  mark  is  left. 

We  might  use  silver  nitrate  in  photography,  but  the  silver 
halogen  compounds  (silver  chloride,  bromide,  and  iodide) 
are  better,  as  they  are  more  sensitive  to  light,  and  are  in- 
soluble. 

Principles  of  photography.  When  silver  nitrate  is  mixed 
with  a  soluble  chloride,  as  sodium  chloride,  a  precipitate  of 
insoluble  silver  chloride  is  formed. 

AgNO3  +  NaCl  -+  AgCl  +  NaNO3 

This  silver  chloride  is  a  white  insoluble  compound  that 
turns  deep  violet  on  exposure  to  light. 

To  make  a  better  photograph  of  our  leaf  than  we  could 
make  by  bleaching  our  colored  paper,  we  might  first  soak 
a  piece  of  filter  paper  in  salt,  and  then  in  a  solution  of  silver 
nitrate.  In  this  way  silver  chloride  is  precipitated  right 
in  the  paper  fibers.  If  now  this  paper  is  exposed  to  light 
with  the  leaf  over  it,  the  paper  blackens  except  where  pro- 


168  CHEMISTRY   IN   THE    HOME 

tected  from  light  by  the  leaf,  and  so  a  photograph  of  the 
leaf  is  obtained. 

This  process  is  also  unsatisfactory,  because,  even  though 
we  keep  the  photograph  in  a  dark  drawer,  it  will  eventually 
all  turn  black,  and  the  picture  disappear.  A  final  step  in 
the  process  is  necessary  to  make  the  print  permanent. 
Silver  chloride  is  soluble  in  sodium  thiosulphate,  commonly 
called  sodium  hyposulphite,  which,  in  turn,  is  shortened  by 
photographers  to  "  hypo."  If  then  the  print  is  soaked  in 
hypo,  the  silver  chloride  that  has  not  been  acted  on  by  the 
light  will  dissolve.  No  compound  that  is  sensitive  to  light 
will  then  be  left  in  the  paper,  that  is,  the  print  will  be  per- 
manent. 

The  picture  will,  however,  be  reversed  as  regards  light  and 
shade.  It  will  form  what  the  photographer  calls  a  nega- 
tive. 

In  order  to  secure  a  correct  reproduction  of  the  original, 
both  light  and  shade  must  be  again  reversed.  This  may  be 
done  by  exposing  a  fresh  piece  of  silver  chloride  paper  under 
the  negative.  Wherever  the  negative  is  black  (opaque), 
there  the  paper  will  be  protected  from  the  light,  and  so  will 
remain  colorless,  while  the  translucent  parts  of  the  negative 
will  transmit  the  light,  and  the  paper  under  them  will  turn 
dark.  Thus  what  is  light  in  the  negative  will  be  dark  in  the 
copy.  That  is,  a  positive,  or  correct,  reproduction  of  the 
leaf  will  be  obtained. 

Developing  the  negative.  Silver  bromide  and  iodide 
may  be  obtained  by  precipitating  silver  nitrate  with  a  solu- 
ble bromide  or  iodide. 

AgN03  +  KBr  ->  AgBr  |  +  KNO3 
AgNO3  +  NH4I  ->  Agl    +  NH4NO3 


PHOTOGRAPHY  169 

They  are  bodies  much  like  silver  chloride,  but  are  even  more 
sensitive  to  the  action  of  light.  Light  does  not  discolor 
them  as  rapidly  as  it  does  the  chloride,  but  a  brief  exposure 
to  light  causes  a  chemical  change  in  them  that,  once  started, 
can  be  continued  by  the  use  of  what  is  known  as  a  developer. 
The  exact  chemistry  of  the  operation  is  very  complex;  it 
will  be  sufficient  if  you  understand  the  following. 

When  light  falls  upon  silver  bromide  or  silver  iodide  in 
the  presence  of  organic  matter,  as  gelatin,  it  causes  a  change 
that  is  not  well  understood.  The  eye  can  see  no  change, 
yet  when  a  developer  (reducing  agent)  is  added  the  affected 
silver  compound  is  reduced  to  metallic  silver.  The  silver 
bromide  or  iodide  that  has  not  been  exposed  to  light  is 
not  reduced  by  the  developer.  In  this  way  the  latent 
image,  as  it  is  called,  is  rendered  visible  during  develop- 
ment. 

The  photographic  plate  that  you  buy  is  made  by  slowly 
adding  silver  nitrate  to  the  hot  solution  of  a  bromide 
and  iodide  in  gelatin.  This  precipitates  silver  bromide 
and  iodide  as  a  fine  powder.  The  character  of  the  plate 
is  determined  by  varying  the  proportion  of  the  iodide  to  the 
bromide.  The  melted  emulsion  is  then  spread  on  glass 
plates.  The  gelatin  cools,  sets,  and  the  plate  is  then  dried. 
If  a  film  is  to  be  made,  the  same  process  is  carried  out,  except 
that  the  emulsion  is  coated  on  a  transparent  film  of  celluloid. 
As  the  plates  are  sensitive  to  ordinary  light,  all  of  these 
operations  must  be  carried  on  in  a  dim  red  light. 

The  photographic  plate  thus  prepared  is  then  exposed  in 
the  camera.  Wherever  light  falls  upon  it,  the  silver  com- 
pound is  altered  in  such  a  way  that  when  the  plate  is  put 
into  the  developer,  which  is  some  reducing  agent,  the  de- 
veloper converts  the  altered  silver  compound  to  metallic 


170 


CHEMISTRY   IN   THE   HOME 


silver.  Since  the  chemical  action  of  light  is  proportional 
to  the  amount  of  light  that  falls  upon  the  plate,  we  obtain, 
on  developing,  a  plate  which  gives  a  reproduction  of  the 
light  and  shade  of  the  original,  but  a  reproduction  in  which 
light  and  shade  are  reversed,  that  is,  a  negative  (Fig.  58). 


The  positive. 


The  negative. 

FIG.  58.  —  Madame  Curie,  discoverer  of  radium.     The  light  parts  of  the 
original  are  dark  in  the  negative. 

To  illustrate :  suppose  we  are  photographing  a  person  wear- 
ing a  black  dress  with  a  white  collar.  The  white  collar 
will  reflect  much  light  to  the  plate.  Where  the  image  of 
this  collar  falls  on  the  plate,  there  will  be  much  chemical 
action,  and  on  developing  we  shall  have  a  black  deposit 
representing  the  white  collar.  The  dress,  being  black,  will 
reflect  only  a  little  light  to  the  plate ;  as  a  result  the  chemical 
action  will  be  feeble,  and  on  developing  only  a  little  silver 


PHOTOGRAPHY  171 

will  be  reduced.  The  image  of  the  black  dress  will  there- 
fore be  almost  transparent  in  the  negative. 

Fixing  the  negative.  To  render  the  negative  permanent, 
it  is  then  soaked  in  a  solution  of  sodium  thiosulphate,  or 
hypo.  This  dissolves  the  silver  salts  that  have  not  been 
acted  upon  by  the  developer,  leaving  nothing  in  the  film  but 
metallic  silver.  This  silver  is  in  such  a  fine  state  of  division 
that,  instead  of  looking  bright,  as  you  might  expect,  it  is 
black.  On  washing  the  hypo  out  of  the  film  and  drying  the 
plate,  we  have  the  finished  negative.  As  this  consists  of  silver 
particles  embedded  in  gelatin,  there  is  no  reason  to  suppose 
that  it  will  not  last  forever,  if  it  is  kept  dry  and  is  not  broken. 

Photographing  colors.  The  amount  of  chemical  action 
on  silver  salts  produced  by  light  depends  on  not  only  the 
amount  of  light,  but  also  its  color.  The  silver  compounds 
are  only  slightly  sensitive  to  red  light,  while  they  are  very 
sensitive  to  blue  light.  This  makes  trouble  in  photographing. 
A  white  dress  having  both  pale  blue  and  pink  dots  on  it 
will  illustrate  this.  To  the  eye  both  pink  and  blue  may  seem 
to  be  equally  bright.  Since,  however,  silver  salts  are  much 
more  sensitive  to  blue  than  to  pink,  on  photographing  the 
dress  the  pink  dots  will  reproduce  almost  black,  while  the 
pale  blue  will  reproduce  almost  white.  This  causes  the 
photograph  of  the  dress  to  look  unnatural.  The  same  diffi- 
culty occurs  in  photographing  flowers ;  some  colors  reproduce 
too  light,  others,  too  dark. 

The  difficulty  may  be  overcome  by  adding  certain  dyes 
to  the  coating  on  the  plate.  These  dyes  make  the  plate  sen- 
sitive to  all  the  colors.  Such  plates  are  called  panchromatic. 
They  can  be  made  to  reproduce  all  colors  satisfactorily, 
but  are  difficult  to  handle,  as  they  are  sensitive  even  to  the 
red  light  of  the  dark  room. 


172  CHEMISTRY   IN   THE   HOME 

Photographic  prints.  An  easy  way  to  obtain  a  print 
showing  light  and  shade  as  in  the  original  is  to  expose  under 
the  negative  a  piece  of  paper  having  on  its  surface  the  same 
kind  of  coating  that  is  on  the  ordinary  plate,  but  so  modified 
as  to  be  less  sensitive  to  light.  On  exposure  to  light,  wherever 
the  negative  is  opaque,  as  the  image  of  a  white  collar, 
little  light  will  pass  through  the  negative  to  the  paper  and 
little  chemical  action  will  take  place.  Wherever  the  nega- 
tive is  transparent,  as  under  the  image  of  the  black  dress, 
much  light  will  pass  through,  and  there  will  be  a  large 
amount  of  chemical  action  on  the  silver  salt.  On  develop- 
ing, in  the  same  way  that  the  negative  is  developed,  an  image 
in  metallic  silver  is  obtained,  but  this  time  the  light  and 
shade  are  the  reverse  of  those  in  the  negative.  This  second 
reversal  will  bring  objects  to  their  natural  shading.  The 
white  collar  will  be  white  and  the  black  dress  black. 

The  print  must  now  be  placed  in  hypo  to  fix  it,  that  is, 
to  dissolve  the  unaltered  silver  compounds,  and  on  washing 
and  drying  will  be  permanent.  "  Velox  "  and  "  Cyko  "  are 
papers  of  this  description. 

Blue  prints.  Another  common  way  of  making  positives 
is  by  the  use  of  blue-print  paper.  The  use  of  this  paper 
depends  upon  two  facts.  First,  ferric  compounds,  on  ex- 
posure to  light,  especially  in  the  presence  of  organic  matter, 
are  easily  reduced  to  ferrous  compounds.  Second,  potas- 
sium ferricyanide  gives  no  precipitate  with  ferric  com- 
pounds, but  gives  a  bright  blue  precipitate  with  ferrous 
compounds. 

A  solution  containing  ferric  ammonium  citrate  and 
potassium  ferricyanide  is  prepared  and  coated  on  the  sur- 
face of  white  paper.  This  is  dried.  If  it  is  placed  in  water, 
the  coating  will  dissolve,  and  leave  nothing  but  a  sheet  of 


PHOTOGRAPHY  173 

white  paper.  But  let  us  place  a  sheet  of  this  prepared  paper 
under  the  negative  that  we  have  made.  The  image  of  the 
white  collar  being  opaque  will  not  allow  light  to  pass,  and 
there  the  coating  will  remain  in  its  original  condition.  Under 
the  image  of  the  black  dress,  which  is  transparent,  the  light 
will  act  on  the  coating  and  reduce  the  ferric  iron  to  ferrous. 
If  now  we  put  the  paper  into  water,  the  ferrous  iron  and  the 
ferricyanide  will  react,  forming  a  blue  precipitate,  which 
will  color  the  paper  blue.  We  shall  then  have  a  picture 
(positive)  in  blue.  Such  paper  is  cheap,  and  easily  pre- 
pared at  home.  It  has  the  disadvantage  of  requiring  a 
long  exposure  to  light,  and  of  giving  a  print  that  is  some- 
what lacking  in  half  tones.  The  color,  too,  is  not  suitable 
for  many  subjects. 

Printing-out  papers.  Still  another  kind  of  photographic 
paper  is  the  so-called  "  printing-out  paper "  (P.  O.  P.), 
of  which  "  Solio  "  is  an  example.  It  consists  of  paper 
coated  with  gelatin  containing  silver  chloride.  It  is  simi- 
lar to  blue-print  paper  in  requiring  a  strong  light  for  exposure, 
and  in  allowing  the  progress  of  the  process  of  printing  to 
be  followed  by  inspecting  the  print  from  time  to  time. 
The  image  is  formed  directly  by  the  action  of  the  sunlight, 
no  developer  being  required,  therefore,  to  make  it  visible, 
as  in  the  case  of  gaslight  papers. 

The  paper  is  fixed  by  means  of  the  usual  hypo  bath,  fol- 
lowed by  a  final  washing  in  water.  But  the  image  thus 
produced  has  a  disagreeable  brick-red  color,  so  it  is  customary 
to  give  the  image  a  more  pleasing  tone.  This  coloring  or 
toning  process,  as  it  is  called,  is  accomplished  by  placing 
the  print  after  removal  from  the  printing  frame  in  a  solution 
of  chloride  of  gold.  Here  the  silver  particles  are  gold  plated 
to  any  desired  degree,  the  brick-red  color  changing  first  to 


174  CHEMISTRY   IN   THE   HOME 

a  rich  brown,  and  then  to  a  purple  tone.  When  the  desired 
tone  is  reached,  the  print  is  fixed  in  hypo,  then  thoroughly 
washed,  and  dried. 

SUMMARY 

A  photographic  plate  consists  of  a  coating  of  gelatin  containing 
silver  salts  on  a  transparent  glass  or  celluloid  support.  On 
exposure  to  light  and  developing,  the  silver  salt  is  reduced  to 
metallic  silver.  On  fixing  in  hypo,  we  obtain  a  negative. 

A  positive  print  can  be  made  by  exposing  a  piece  of  paper  coated 
with  a  silver  salt  in  gelatin  under  the  negative,  developing, 
and  fixing. 

Exercises 

1.  Why  is  it  necessary  to  fix  the  negative? 

2.  Why  do  silver  prints  sometimes  fade  ? 

3.  Why  do  you  wash  the  negative  after  fixing? 

4.  Apples  are  sometimes  sold  that  have  the  name  of  the  grower 
in  green  letters  on  the  skin,  while  the  rest  of  the  skin  of  the  apple  is 
red.     Can  you  explain  how  these  could  be  made  ? 

5.  Could  you  make  a  photograph  using  nothing  but  newspaper  ? 

6.  In  photographing  a  landscape,  why  is  it  that  faint  clouds 
often  do  not  show  on  the  negative? 

7.  Why  does  the  "  proof  "  sent  by  the  photographer  fade? 


CHAPTER  XVII 
CARBON   AND    ITS    COMPOUNDS 

Organic  chemistry  defined.  One  of  the  facts  that  every 
cook  learns  early  in  her  experience  is  that  all  foods  char 
when  they  are  heated  too  hot.  This  is  because  all  of  these 
compounds  contain  carbon.  Since  all  of  these  compounds 
that  are  made  by  living  things  come  from  organisms,  we 
call  them  organic,  and  their  chemistry,  organic  chemistry. 
We  have  learned  to  make  many  of  these  compounds  in  the 
laboratory.  There  is  no  real  difference  between  the  sugar 
made  in  the  sugar  cane  and  the  sugar  made  in  the  labora- 
tory, so  we  must  call  them  both  organic.  Instead,  then,  of 
defining  organic  chemistry  as  the  study  of  the  chemistry 
of  living  organisms,  it  is  preferable  to  say  that  organic  chem- 
istry is  the  chemistry  of  carbon  compounds. 

Forms  of  carbon.  The  element  carbon  is  found  widely 
distributed  in  nature  in  a  number  of  forms,  as  the  diamond, 
graphite,  and  coal.  That  these  very  dissimilar  substances 
are  all  really  carbon  is  proved  by  the  fact  that,  when  they 
burn,  nothing  but  carbon  dioxide  is  formed  except  in  the 
case  of  coal,  which  gives  some  other  products  because  of 
certain  impurities  in  the  coal.  You  will  recall  the  fact  that 
phosphorus  occurs  as  both  red  and  white  phosphorus,  two 
different  forms  having  quite  different  properties,  yet  both 
forms  can  be  shown  to  contain  nothing  but  phosphorus 
atoms,  and  each  can  be  readily  converted  into  the  other. 

175 


176 


CHEMISTRY   IN   THE    HOME 


Chemists  explain  this  by  the  fact  that  although  both  red 
and  white  phosphorus  molecules  contain  nothing  but  phos- 
phorus atoms,  the  number 
of  atoms  in  the  two  mole- 
cules is  different.  Oxygen 
also  exists  in  two  forms, 
ordinary  oxygen  and  ozone, 
having  quite  different  physi- 
cal and  chemical  properties. 
The  same  fact  explains  this. 
Ordinary  oxygen  is  O2,  while 
ozone  is  O3  Such  different 
forms  of  the  same  element 
are  called  allotropic  modifi- 
cations. 

Carbon  is  one  of  the 
elements  that  exist  in  a 
number  of  these  allotropic 
modifications.  It  occurs  in 
two  main  typical  forms : 
crystalline  carbon,  includ- 
ing the  diamond  and  graph- 
ite, and  noncrystalline,  or 
amorphous  carbon,  includ- 
ing lampblack  and  coal. 

Formation  of  coal.  Ages 
ago  the  distribution  of  land 
and  water  on  the  earth  was 
very  different  from  what  it 
is  to-day.  Nor  was  the  air 
of  its  present  composition, 

FIG.  59.  —  Coal  series,     a,  peat ;  b,  lig-  .  . 

nite  ;  c,  bituminous ;  d,  anthracite.         as  it  contained  more  Carbon 


CARBON   AND   ITS   COMPOUNDS  177 

dioxide  and  water  vapor.  By  studying  the  rocks,  and 
the  fossils  contained  in  them,  geologists  have  given  us 
a  good  idea  of  the  conditions  prevailing  at  that  far-distant 
time.  For  instance,  what  is  now  the  central  part  of  Penn- 
sylvania was  then  a  low,  swampy  country.  Its  climate 
was  much  warmer  than  now,  and,  as  the  air  contained 
large  quantities  of  carbon  dioxide  and  water,  both  of  which 
are  so  important  to  growing  plants,  vegetation  grew  with 
almost  tropical  luxuriance.  Ferns,  for  instance,  were  often 
thirty  feet  high  and  ten  inches  in  diameter,  as  shown  by 
their  fossil  remains.  As  this  dense  vegetation  growing  on 
low,  swampy  land  died,  it  fell  into  the  water.  There  it 
could  not  easily  decay  because  of  the  lack  of  oxygen.  In- 
stead, as  more  and  more  accumulated,  it  turned  into  a  solid 
mass  similar  to  the  peat  of  the  present  day.  This  accumu- 
lation of  organic  matter  finally  became  buried  deep  beneath 
the  surface  of  the  earth,  where  pressure  and  heat  made 
it  still  more  compact.  This  formed  what  we  now  call 
brown  coal,  and  large  deposits  of  this  exist  all  over  the 
world.  Brown  coal  is  also  called  lignite. 

As  the  heat  and  pressure  were  increased,  still  more  of  the 
volatile  matter  was  driven  from  the  brown  coal,  and  soft, 
or  bituminous,  coal  resulted.  In  a  few  places  the  process 
has  been  carried  one  step  further,  and  hard,  or  anthracite, 
coal  formed.  In  much  of  the  soft  coal  we  find  the  imprint 
of  leaves  and  the  remains  of  tree  trunks,  showing  its  vege- 
table origin.  When  soft  coal  is  cut  into  very  thin  slices,  it 
is  even  possible  to  see  the  cells  of  the  wood  from  which  it 
was  made. 

Wood  to  coal.  Wood  contains  much  volatile  matter, 
and  the  progressive  change  of  the  wood  (vegetable  matter) 
into  hard  coal  was  essentially  the  driving  off  of  this  volatile 


178 


CHEMISTRY   IN   THE   HOME 


matter,  leaving  only  carbon.  Hard  or  anthracite  coal  is, 
then,  essentially  carbon.  It  contains  in  addition  the  mineral 
matter  of  the  original  vegetation,  and  this  is  left  as  an  ash 
when  the  coal  is  burned.  These  facts  will  explain  to  you 
why  there  is  so  much  brown  coal,  less  bituminous  coal,  and 
very  little  anthracite  coal.  Originally  it  was  all  brown  coal. 
In  a  number  of  places  the  conditions  were  favorable,  and  the 
brown  coal  was  changed  into  bituminous  coal,  while  only 
in  a  few  localities  did  the  change  continue,  resulting  in  the 
formation  of  anthracite.  This  gradual  change,  resulting  in 
an  increase  in  the  amount  of  carbon  and  a  decrease  in  the 
amount  of  volatile  matter,  is  well  shown  in  the  following 
table : 1 


FUEL 

PER  CENT  OF  (EXCLUDING 
ASH  AND  MOISTURE) 

PER  CENT 
OF  ASH 

CALORIFIC 
VALUE  PER 
GRAM  IN 
CALORIES 

C 

H 

0 

N 

Wood.     .     .     . 

45 

6 

48 

1 

1.5 

2700 

Peat     .... 

60 

6 

32 

2 

5-20 

3500 

Brown  coal  . 

70 

5 

24 

1 

3-20 

6000 

Bituminous  . 

82 

5 

12 

1 

1-15 

8000 

Anthracite    .     . 

94 

3 

3 

— 

6 

8000 

Charcoal  . 

95 

1.7 

3.4 

— 

4 

8080 

Coke.  .... 

96 

0.7 

2.5 

1 

3-11 

7700 

Illuminating  gas.  When  soft  coal  is  heated  out  of  con- 
tact with  the  air,  the  volatile  compounds  in  it  are  largely 
broken  up  into  illuminating  gas,  coal  tar,  and  ammonia, 
while  most  of  the  carbon  remains  in  the  retort  in  the  form 
of  a  hard,  porous  mass  called  coke. 

1  Inorganic  Chemistry,  Smith. 


CARBON   AND   ITS   COMPOUNDS 


179 


Commercially,  this  operation  is  carried  out  in  long  slender 
retorts.  The  gases  produced  are  led  into  water,  where  most 
of  the  ammonia  and  much  of  the  coal  tar  dissolves.  The 
gases  are  then  led  into  large  pipes  called  condensers,  where 
the  remaining  coal  tar  and  liquid  hydrocarbons  condense. 
To  remove  the  last  traces  of  ammonia  and  coal  tar,  the 
gases  are  then  passed  through  towers  filled  with  coke,  kept 
wet  with  water.  Here  the  remainder  of  the  ammonia  and 
coal  tar  is  removed.  It  is  next  passed  over  iron  oxide,  to 


FIG.  60.  —  Coal  gas  manufacture. 

remove  any  sulphur  compounds  present  and  illuminating 
gas  remains.  This  is  the  old-fashioned  process  (Fig.  60). 
Some  gas  is  still  produced  by  it,  but  more  is  produced  by 
another  method,  which  will  be  explained  in  the  next  chapter 
(p.  192). 

The  water  solution  of  the  ammonia  is  used  commercially 
as  a  source  of  ammonia,  while  the  coal  tar  contains  many 
valuable  carbon  compounds,  as  benzol,  used  in  the  manu- 
facture of  aniline  dyes,  and  naphthalene,  used  for  moth  balls. 
In  Pennsylvania,  soft  coal  is  destructively  distilled  in  large 

WEED    CHEMISTRY 12 


180 


CHEMISTRY   IN   THE    HOME 


ovens  for  the  sake  of  the  coke,  which  is  used  largely  in  the 
production  of  pig  iron  in  blast  furnaces. 

Petroleum.  In  many  sections  of  our  country,  as  in  Penn- 
sylvania, Texas,  and  California,  far  below  the  surface  of 

the  earth,  large  deposits  of 
a  thick,  oily  liquid  exist. 
This  liquid,  called  crude  pe- 
troleum, is  obtained  by  drill- 
ing wells  (Fig.  61).  Crude 
petroleum  is  not  made  up 
of  one  chemical  compound, 
but  contains  a  large  number 
of  compounds,  and  these  are 
separated  and  prepared  for 
use  by  distillation. 

The  thick,  oily  liquid  is 
placed  in  large  stills,  capa- 
ble of  holding  500  barrels 
or  more  of  the  oil  (Fig.  62). 
Heat  is  then  applied,  and 
the  more  volatile  liquids 
boil  off  first.  The  distillation 
products  are  called  naphtha, 
benzine,  or  gasoline.  After 

FIG.  61. -A  spouting  oil  well.  these    have   been   driven    °ff> 

the   temperature    rises    and 

kerosene  distills.  Then  come  light,  followed  by  heavy, 
lubricating  oils,  and  finally  nothing  but  pitch  remains  in 
the  still. 

Each  of  these  products  is  a  mixture  of  various  carbon 
compounds.  From  the  lubricating  oil  the  waxy  solids 
vaseline  and  paraffin  are  produced.  The  amount  of  pe- 


CARBON   AND   ITS   COMPOUNDS 


181 


troleum  produced  is  very  large,  as  will  be  seen  from  the 
table  below : 

WORLD'S  PRODUCTION  OF  PETROLEUM  IN  1912 


COUNTRY 

QUANTITY. 
METRIC  TONS 

PERCENTAGE 
OF  TOTAL 

United  States 

29  615  096 

63  25 

Russia 

9,317,700 

19.37 

IMexico                                     .... 

2,207,762 

4.71 

1,478,132 

3.09 

Rournania 

1,806942 

3.70 

O  alioi  a. 

1,187,007 

2.43 

India                               

989,801 

2.03 

Other  countries  

674,285 

1.42 

Total 

47  276  725 

100.00 

FIG.  62.  —  Petroleum  stills. 

Natural  gas.  We  often  find  a  combustible  gas  associated 
with  crude  petroleum.  This  gas,  called  natural  gas,  some- 
times exists  in  such  quantities  that  the  oil  wells  furnish 
enough  gas  to  warm  and  light  whole  cities.  Pittsburgh  is 
near  an  oil  field  that  produced  large  quantities  of  this  natural 


182  CHEMISTRY   IN   THE   HOME 

gas,  and  for  years,  instead  of  using  artificial  illuminating  gas, 
the  city  used  this  natural  gas.  Burned  in  ordinary  gas 
burners  it  does  not  give  a  bright  light,  but  is  well  suited  for 
use  with  Welsbach  burners,  and  in  gas  stoves. 

Charcoal  and  bone  black.  When  wood  is  heated  out  of 
contact  with  the  air  (destructively  distilled),  the  volatile 
matters  are  driven  off.  Many  products  are  thus  obtained,  as 
wood  alcohol,  acetic  acid,  and  combustible  gases,  while  char- 
coal is  left  in  the  retort.  Not  only  wood,  but  any  organic 
matter  can  be  destructively  distilled,  and  a  charcoal  produced, 

If  bones  are  thus  treated,  bone  charcoal,  called  bone 
black,  is  obtained.  This  has  the  power  of  absorbing 
many  times  its  own  volume  of  gas.  If  this  bone  charcoal 
is  exposed  to  the  air,,  it  absorbs  much  oxygen,  and  because 
of  this  it  can  be  used  to  oxidize  noxious  odors.  It  is  also 
used  in  the  manufacture  of  sugar  to  remove  the  brown  color 
of  the  sugar  sirup.  It  is  an  interesting  experiment  to  shake 
together  bone  charcoal  (bone  black)  and  a  solution  of  hydro- 
gen sulphide,  the  substance  that  gives  rotten  eggs  their 
characteristic  odor.  The  odor  is  quickly  destroyed,  show- 
ing how  energetic  the  action  of  the  bone  black  is.  The 
best  way  to  prepare  pure  carbon  is  to  char  sugar,  thus 
obtaining  sugar  charcoal. 

Lampblack.  Lampblack  is  made  by  the  incomplete 
combustion  of  materials  rich  in  carbon.  Natural  gas,  for 
instance,  is  burned  in  such  a  way  that  the  flame  strikes  an 
iron  surface  kept  cool  by  water  flowing  over  it.  Under 
these  conditions,  the  compounds  present  in  the  gas  decom- 
pose, forming  carbon  and  hydrogen.  The  hydrogen  burns, 
forming  water,  but  the  carbon  that  forms  in  the  flame  is 
cooled  below  its  kindling  point  before  it  can  burn,  by  the 
cold  iron  against  which  it  strikes,  and  is  deposited  on  the  iron. 


CARBON   AND   ITS   COMPOUNDS 


183 


FIG.  63.  —  Commercial  production  of 
lampblack. 


A  scraper  removes  the  carbon  from  the  iron,  and  it  forms 
the  lampblack  of  trade.  It  is  largely  carbon,  but  contains 
some  tarry  matters. 
It  finds  many  uses,  as 
in  black  paints,  in 
printer's  ink,  and  in 
darkening  the  color  of 
cement  sidewalks. 

Graphite.  Our  "lead 
pencils "  are  made 
from  another  allotropic 
form  of  carbon,  called 
graphite,  plumbago,  or 
black  lead.  We  are 
not  sure  just  how  it 
has  been  formed  in 
nature,  but  some  chemists  think  that  it  has  been  formed  by 
carrying  the  heating  and  pressure  of  coal  a  step  beyond  the 
point  where  anthracite  is  produced. 

Graphite  occurs  as  grains  in  rock,  and  is  crystalline,  form- 
ing six-sided  plates.  It  is  a  black,  greasy-feeling  substance, 
having  a  metallic  luster.  It  is  used  in  making  crucibles,  as  a 
lubricant,  and  in  lead  pencils.  In  spite  of  its  seeming  soft- 
ness, the  individual  particles  of  graphite  are  very  hard,  as  is 
shown  by  the  way  the  iron  tools  used  in  cutting  it  wear  out. 
Because  of  its  greasy  nature,  it  clings  readily  to  metals,  and  is 
therefore  used  as  a  protective  coating.  Common  stove  polish, 
for  instance,  is  largely  graphite. 

The  various  grades  of  hardness  of  lead  pencils  are  obtained 
by  using  various-sized  particles  of  graphite,  and  binding 
them  together  with  clay.  Large  particles  and  little  clay 
gives  a  very  soft  pencil. 


184  CHEMISTRY  IN  THE   HOME 

Chemists  have  found  it  possible,  by  the  help  of  the  electric 
furnace,  to  prepare  graphite  artificially,  and  large  quantities 
are  now  made  at  Niagara  Falls,  where  electric  power  is  cheap. 
This  synthetic  graphite  is  used  in  making  the  electrodes  for 
electric  furnaces. 

Diamond.  The  diamond  occurs  in  Brazil,  India,  and  South 
Africa.  It  is  valuable  as  a  jewel  because  of  its  rarity,  its 
hardness  (it  is  the  hardest  substance 
known),  its  luster,  and  its  effect  on 
light.  You  have  all  looked  through 
a  glass  prism  and  seen  that  rays  of 
light  are  bent,  on  passing  through  it, 
and  that  the  edges  of  objects  seen 
through  it  are  fringed  with  colored 
light.  The  diamond  will  bend  and 
disperse  white  light  much  more  than 
glass  will,  and  it  is  this  high  refrac- 
tion that  gives  the  fire  and  color  to 
the  cut  stone.  A  piece  of  glass,  cut 
in  the  same  form  as  a  diamond,  may 
be  equally  transparent,  but  the  play 
of  color  will  be  lacking,  and  the 
beauty  of  the  diamond  is  not  found 
in  the  imitation. 

FIG.  64  -Crystal  forms  of         When    firgt    found     diamonds    are 

natural  diamonds. 

often  shaped  like  an  octahedron  (Fig. 

64).  They  have  little  beauty,  and  must  be  cut  in  a  regular 
form  in  order  to  bring  out  their  hidden  splendor.  The  stone 
is  so  hard  that  it  cannot  be  ground  with  any  of  the  usual 
abrasives.  It  must  be  cut  and  polished  by  the  use  of  dia- 
mond dust. 
The  diamond  that  is  to  be  cut  is  first  set  into  a  lump  of 


CARBON  AND   ITS  COMPOUNDS  185 

solder,  fastened  to  the  end  of  a  short  stick.  The  part  of 
the  diamond  that  is  to  be  ground  off  is  then  laid  on  an  iron 
plate  that  can  be  rotated,  and  the  plate  smeared  with 
diamond  dust  mixed  with  oil.  The  iron  plate  is  rotated  and 
the  diamond  is  very  slowly  worn  away  by  rubbing  on  the 


FIG.  65.  —  Sorting  diamonds. 

diamond  dust.  When  one  face  of  the  stone  has  been  thus 
polished,  the  solder  is  heated,  the  diamond  taken  out,  and 
put  back  so  as  to  expose  another  face  that  is  to  be  polished. 
In  this  way,  face  after  face  is  polished,  until  the  stone  has  its 
finished  form.  This  takes  a  long  time,  requires  skilled  labor, 
and  so  adds  much  to  the  cost.  Diamond  dust  is  made  by 
crushing  small  imperfect  stones,  for,  although  the  diamond  is 


186  CHEMISTRY   IN   THE   HOME 

so  hard,  it  is  also  very  brittle.  It  is  not  an  unusual  thing 
for  a  diamond  to  break  if  dropped  on  a  stone  floor. 

The  value  of  a  diamond  depends  on  its  freedom  from  flaws, 
the  perfection  of  the  cut,  the  color,  and  its  fire.  Diamonds 
of  many  colors  are  found,  pink,  blue,  brown,  and  yellow,  as 
well  as  white.  A  stone  that  has  a  decided  color  is  often  more 
valuable  than  a  white  stone,  but  a  faint  tinge  of  yellow  kills 
the  fire  of  the  stone,  and  decreases  its  value  greatly. 

The  largest  diamond  that  has  been  found  was,  before  cut- 
ting, the  size  of  a  man's  fist,  and  weighed  621  grams,  or  more 


FIG.  66.  —  Kohinoor  diamond.     Weight  of  first  cut,  186.5  carats; 
recut,  125  carats. 

than  one  pound.  The  famous  Kohinoor,  one  of  the  crown 
jewels  of  England,  weighs  22  grams  (Fig.  66).  In  Brazil, 
black  diamonds  are  found.  These  are  of  no  value  as  jewels, 
but,  owing  to  their  great  hardness,  they  are  used  to  point 
drills  for  drilling  hard  rock. 

The  weight  of  a  diamond  is  always  given  in  carats.  The 
new  international  carat  weighs  200  milligrams.  The  value 
of  a  diamond  increases  more  rapidly  than  its  weight.  If  a 
first-class  cut  stone  of  |  carat  is  worth  100  dollars,  a  stone 
weighing  one  carat  will  be  worth  275  dollars,  and  one  of  two 
carats'  weight  will  be  worth  650  dollars.  The  cost  of  a  one- 


CARBON  AND   ITS  COMPOUNDS  187 

carat  diamond  may  be  anywhere  between  one  hundred  and 
three  hundred  dollars,  depending  on  the  color,  perfection  of 
cut,  and  fire  of  the  stone. 

Small  diamonds  have  been  made  synthetically,  but  they 
are  only  chemical  curiosities,  as  they  are  costly,  and  very 
small. 

SUMMARY 

Carbon  has  three  allotropic  forms  :  diamond,  graphite,  lampblack. 

Coal  was  formed  by  the  partial  oxidation  of  vegetable  matter  out  of 
contact  with  the  air. 

Bone  black  is  an  important  form  of  carbon,  much  used  in  decoloriz- 
ing impure  solutions. 

Sugar  charcoal  is  a  pure  form  of  carbon  easily  prepared. 

Crude  petroleum  yields  gasoline,  benzine,  naphtha,  kerosene, 
lubricating  oils,  vaseline,  and  paraffin. 

Graphite  is  used  in  lead  pencils,  stove  polish,  crucibles,  and  elec- 
trodes for  electric  furnaces. 

The  diamond  is  the  hardest  substance  known. 

Exercises 

1.  How  can  you  prove  that  graphite  is  carbon? 

2.  Why  does  a  soft-coal  fire  give  a  much  brighter  light  than  a 
hard-coal  fire? 

3.  Why  is  charcoal  sometimes  placed  in  a  refrigerator? 

4.  Why  does  bone  black  lose  its  efficacy  after  long  use? 

5.  Is  coal  being  made  at  the  present  time  ? 


CHAPTER  XVIII 


THE    OXIDES    OF    CARBON 

Preparation  and  properties  of  carbon  dioxide.    Whenever  a 
carbon  compound  burns  with  a  free  supply  of  air,  a  colorless 

gas,  carbon  dioxide, 
CO2,  is  formed.  The 
pure  gas  is  prepared 
by  the  action  of  an 
acid  on  a  carbonate. 
Place  marble  chips 
(calcium  carbonate) 
in  a  generator,  similar 
to  the  one  used  in 
preparing  hydrogen 
(Fig.  67).  Add  hy- 
drochloric acid 

through  the  thistle  tube.  A  violent  evolution  of  gas  takes 
place,  and  this  gas  can  be  collected  by  water  displacement. 

CaC03  +  2  HC1  ->  CaCl2  +  H2O  +  CO2  f 

Any  carbonate  may  be  used  instead  of  marble,  and  any  acid 
that  will  dissolve  the  carbonate,  as : 

Na2C03  +  H2SO4  -*-Na*SO4  +  H2O  +  CO2 1 

Examination  of  the  carbon  dioxide  thus  prepared  shows  that 
it  is  a  colorless  gas,  without  taste  or  odor.  When  tested  with 
a  lighted  match,  it  does  not  burn  or  support  combustion. 
On  shaking  it  up  with  a  little  water,  it  dissolves,  giving 

188 


FIG.  67.  —  Carbon  dioxide  generator. 


THE    OXIDES   OP   CARBON 


189 


a  very  slightly  sour  solution  that  turns  blue  litmus  red. 
Since  the  solution  of  carbon  dioxide  in  water  gives  an  acid 
reaction  with  litmus,  it  must  in  solution  form  an  acid. 

H2O  +  CO2  -+  H2CO3 

We  name  this  acid  carbonic  acid,  and  the  salts  made  from  it 
carbonates. 

One  thing  that  distinguishes  carbon  dioxide  from  other 
colorless  gases  is  its  specific  gravity.  It  is  about  one  and 
a  half  times  as  heavy  as  air.  This  can  be  shown  in 
a  striking  way  by  placing  a  candle  in  a  glass,  lighting 
it,  and  then  pouring  carbon  dioxide  down  on  it  from  a 
bottle.  Carbon  dioxide  is  so  heavy  that  it  can  be  poured 
like  water ;  it  therefore  fills  the  glass  and  extinguishes  the 
candle. 

Carbon  dioxide  gas  is  often  incorrectly  called  carbonic  acid. 
Of  course  it  cannot  be  an  acid,  as  all   acids  must  contain 
hydrogen.     It  is  only 
when   it  is   dissolved 
in  water  that  it  be- 
comes   an    acid.     It 
may    properly   be 
called    carbonic    acid 
anhydride. 

Uses  of  carbon  ci-   

Oxide.          The       great     FIG.  68.  —  Carbonated  spring  waters  often  de- 

uses  of  carbon  dioxide 

are  in  beverages  and 

as  a  leavening  agent.      Every  drink  that  effervesces,  soda, 

vichy,  root  beer,  etc.,  owes  its  effervescence  to  the  presence 

of  dissolved  carbon  dioxide.     When  you  drink  plain  soda, 

you  are  really  drinking  a  weak  solution  of   carbonic  acid. 


posit  dissolved  solids,  making  a  raised  cone 
from  which  the  water  flows. 


190 


CHEMISTRY   IN   THE   HOME 


Its  use  as  a  leavening  agent  will  be  treated  in  the  following 

chapter  (p.  196). 

In   many   parts   of   the   earth,    spring   waters   naturally 

contain  considerable  amounts  of  this  gas.  The  springs 
at  Saratoga  are  illustrations  of  this,  as  are 
the  Vichy,  Seltzer,  and  Apollinaris  springs. 
Fire  extinguisher.  As  carbon  dioxide 
will  neither  burn  nor  support  burning,  it 
is  used  in  fire  extinguishers.  In  many 
buildings  you  have  seen  copper  cylinders 
with  a  short  hose  coming  from  the  top. 
Examine  one  and  you  will  find  the  direc- 
tions :  "  To  start,  turn  upside  down,  and 
play  on  the  fire."  Their  construction  is 
simple.  The  cylinder  is  filled  with  a 
solution  of  sodium  bicarbonate.  At  the 
top  is  suspended  a  bottle  containing  sul- 
phuric acid.  This  bottle  is  loosely  closed 
with  a  lead  stopper.  On  turning  the 
cylinder  upside  down,  the  stopper  falls 
out  and  the  acid  runs  out.  When  the 
acid  mixes  with  the  sodium  bicarbonate, 

FIG.  69. -Section  of    carbon   dioxide   is   generated.     Some    of 

a  fire  extinguisher. 

this  dissolves  in  the  water,  and  the  rest, 
accumulating  in  the  cylinder,  generates  a  pressure  that  forces 
the  water  and  gas  through  the  hose  upon  the  fire.  They 
are  efficient  if  used  before  the  fire  has  too  great  a  start. 

2  NaHCO.3  +  H2S04  ->  Na2SO4  +  2  H2O  +  2  CO2  f 

Test  for  carbon  dioxide.  It  is  easy  to  test  for  the  presence 
of  carbon  dioxide  by  the  use  of  a  solution  of  calcium  hydroxide, 
called  limewater.  If  a  little  limewater  is  shaken  with  car- 


THE    OXIDES   OF   CARBON  191 

bon  dioxide,  calcium  carbonate  is  formed,  and  the  solution 
turns  milky. 

Ca(OH)2  +  CO2  ->  CaC03 1  +  H2O 

Utilization  of  carbon  dioxide  by  plants.  Every  fire  pro- 
duces large  amounts  of  carbon  dioxide,  animals  breathe  it  out ; 
it  is  one  of  the  products  of  the  decay  of  all  organic  material. 
In  this  way  large  amounts  get  into  the  air.  Plants  then 
utilize  it  as  a  food.  Under  the  influence  of  the  energy  of 
sunlight,  chlorophyll,  the  green  coloring  matter  of  plants, 
makes  starch  from  it.  Much  of  the  oxygen  of  the  carbon 
dioxide  is  not  needed  in  this  process,  and  the  plant  passes  this 
once  more  into  the  air.  In  this  way,  the  amount  of  oxygen 
in  the  air  is  kept  constant. 

Carbon  monoxide.  When  carbon  is  burned  in  an  amount 
of  air  too  small  for  its  complete  combustion,  a  second  oxide 
of  carbon,  carbon  monoxide,  CO,  is  formed.  It  is  a  colorless, 
tasteless,  odorless  gas,  very  slightly  soluble  in  water.  It 
burns  with  a  peculiar  pale  blue  flame,  forming  carbon  dioxide. 

2  CO  +  O2  ->  2  CO2 

Carbon  monoxide  is  a  poisonous  gas,  and  is  all  the  more 
dangerous  because,  owing  to  its  lack  of  odor,  we  have  no 
warning  of  its  presence.  Water  gas,  which  is  the  illuminat- 
ing gas  commonly  in  use,  contains  about  40  %  of  it,  and  it  is 
the  presence  of  this  carbon  monoxide  that  makes  gas  leaks 
so  dangerous. 

The  oxygen  necessary  to  oxidize  our  tissues  is  carried  to 
the  remotest  parts  of  our  body  by  the  red  coloring  matter  of 
the  blood,  called  haemoglobin.  This  combines  in  the  lungs 
with  oxygen,  forming  with  it  a  loose  chemical  compound. 
The  blood  then  carries  the  haemoglobin,  combined  with 
oxygen,  wherever  it  is  needed.  When  this  oxygen  is  given 


192 


CHEMISTRY   IN   THE    HOME 


up  to  oxidize  materials  in  our  body,  carbon  dioxide  is  pro- 
duced as  a  waste  product.  The  blood  carries  this  carbon 
dioxide  to  the  lungs,  where  it  is  exhaled,  and  where  the 
haemoglobin  combines  with  more  oxygen.  Carbon  mon- 
oxide forms  a  stable  compound  with  haemoglobin.  This 
makes  the  combination  of  the  haemoglobin  with  oxygen  im- 
possible, the  body  cannot  obtain  oxygen,  and  we  suffocate. 


FIG.  70.  —  Manufacture  of  water  gas. 

The  taking  up  of  oxygen  by  the  haemoglobin  gives  the  blood 
its  bright  red  color,  while  its  combination  with  carbon  dioxide 
gives  the  blood  a  purple  color. 

Water  gas.  There  are  two  ways  of  making  illuminating 
gas.  The  first,  by  heating  soft  coal  (p.  178).  The  second 
is  by  the  action  of  steam  upon  red-hot  carbon.  Coke  is 
placed  in  large  iron  cylinders  and  air  blown  through  it  until 
the  coke  is  white  hot.  The  air  blast  is  then  shut  off,  and 
steam  blown  through  the  coke.  The  white-hot  coke  reduces 
the  steam,  forming  carbon  monoxide  and  hydrogen. 
H20  +  C  ->•  H2  +  CO 


THE    OXIDES   OF   CARBON  193 

When  the  steam  has  cooled  the  coke  so  that  the  reaction  is 
slow,  air  is  once  more  blown  through  the  coke,  it  is  again 
heated  white  hot,  and  the  process  is  repeated. 

This  mixture  of  hydrogen  and  carbon  monoxide  burns  with 
a  hot  but  colorless  flame.  It  is  suitable  for  use  in  a  gas  stove 
or  a  Welsbach  burner,  but  not  for  use  in  an  ordinary  gas 
burner  for  lighting  purposes.  To  make  it  burn  with  a  lumi- 
nous flame,  it  must  be  mixed  with  the  vapor  of  an  oil  that  will 
decompose  in  the  flame  and  set  carbon  free.  To  do  this,  the 
gas  is  passed  into  the  carburetor,  where  it  is  mixed  with  a 
spray  of  crude  oil.  It  then  passes  to  a  very  hot  chamber 
called  a  superheater,  where  the  mixture  is  made  complete  and 
the  oil  vapors  are  changed  into  permanent  gases. 

The  water  gas  must  then  be  purified  by  passing  it  into  a 
wash  box,  where  it  is  cooled  by  water,  and  some  tarry  products 
that  have  been  formed  are  condensed.  Then  it  goes  to  the 
scrubber,  a  tower  where  the  gas  has  to  rise  through  zigzag 
passages  that  are  kept  wet.  Finally,  it  passes  to  the  con- 
denser pipes,  where  it  is  cooled  to  150°  F.,  and  finally  to  the 
gas  holder. 

The  candle  power  of  the  gas  is  controlled  by  the  amount  of 
oil  that  is  added  to  it.  The  process  is  cheap,  and  the  product 
burns  well  and  gives  a  good  light.  Its  disadvantage  is  the 
poisonous  character  of  the  gas,  due  to  the  large  percentage  of 
carbon  monoxide  that  it  contains.  On  the  average  more 
than  one  person  a  day  dies  in  the  city  of  New  York  through 
inhaling  water  gas. 

Danger  from  furnace  gas.  Carbon  monoxide  is  sometimes 
made  accidentally  in  ordinary  furnaces.  If  the  bed  of  coal  is 
quite  thick,  and  the  amount  of  air  somewhat  limited,  the 
oxygen  of  the  air  will  all  be  used  up  in  the  lower  part  of  the 
fire  in  combining  with  the  burning  carbon  and  forming  carbon 


194  CHEMISTRY   IN   THE   HOME 

dioxide.  This  carbon  dioxide  then  passes  through  the  upper 
part  of  the  fire,  where  the  hot  carbon  reduces  it  to  carbon 
monoxide.  The  carbon  monoxide  thus  produced  burns  on 
the  top  of  the  fire  and  is  the  cause  of  the  flickering  blue  flame 
sometimes  seen  playing  over  the  top  of  an  anthracite  fire. 

SUMMARY 

Carbon  dioxide :  How  produced.  Carbon  dioxide  is  prepared  by 
the  action  of  an  acid  on  a  carbonate.  It  is  formed  by  the 
decay  of  organic  matter,  the  combustion  of  fuels,  and  fermen- 
tation. 

Properties:  Carbon  dioxide  is  a  heavy,  colorless,  tasteless,  odor- 
less gas.     It  does  not  burn  or  support  combustion.      It  dis- 
solves in  water,  forming  carbonic  acid. 
Uses :  Carbon  dioxide  is  used  in  beverages,  as  a  leavening  agent, 

in  fire  extinguishers,  and  as  food  for  plants. 
Test:  Lime  water  is  a  test  for  carbon  dioxide. 
Carbon  monoxide  :    How  produced.     Carbon  monoxide  is  made  by 

heating  carbon  dioxide  with  carbon. 
Properties:    Carbon  monoxide  is  a  colorless,  tasteless,  odorless 

gas.     It  is  a  poison. 

Water  gas  is  a  mixture  of  carbon  monoxide,  hydrogen,  and  gases 
from  crude  oil.  It  burns  with  a  luminous  flame,  and  is  very% 
poisonous. 

Exercises 

1.  The  city  of  New  York  burns  enough  coal  to  convert  all  of  the 
oxygen  of  the  air  over  the  city  into  carbon  dioxide.     Why  do  the 
inhabitants  not  suffocate? 

2.  When  you  open  a  bottle  of  vichy,  the  contents  of  the  bottle 
become  milky  with  gas  bubbles.     Why  ? 

3.  Why  can  we  not  obtain  pure  carbon  dioxide  by  burning  char- 
coal in  the  air  ? 

4.  Why  is  carbon  dioxide  used  in  fire  extinguishers  ? 

5.  Why  is  water  gas  enriched  with  oil  vapors  ? 

6.  Under  what  conditions  may  a  poisonous  gas  be  given  off  from 
the  kitchen  range  ? 


CHAPTER  XIX 
BAKING   POWDERS 

Mechanical  methods  of  leavening  bread.  Bread,  our 
great  staple  food,  and  cakes  and  pastries  with  which  we  tempt 
our  palates,  are  usually  made  light,  to  render  them  more 
palatable  and  digestible.  Bread  is  usually  leavened  by  the 
use  of  yeast  (p.  287).  At  present  we  shall  consider  some 
other  methods  of  gaining  the  same  end. 

Unleavened  bread,  as  used  in  hard-tack,  the  cornmeal 
"  pone  "  of  the  South,  and  the  Scotch  oatmeal  cake,  contains 
few  gas  bubbles.  In  consequence,  it  is  hard,  dry,  and  de- 
mands long  mastication.  To  render  bread  light,  the  dough 
must  contain  a  multitude  of  small  gas  bubbles.  When  the 
dough  is  placed  in  the  oven,  these  expand,  the  dough  in- 
creases in  volume,  and  the  bread  is  made  light. 

There  are  a  number  of  mechanical  means  by  which  this  can 
be  done.  By  vigorously  beating  the  mixture  of  flour  and 
water,  air  bubbles  can  be  entrapped,  and  these  will  make 
the  bread  somewhat  light.  A  thin  dough  must  be  used,  as 
otherwise  the  beating  is  too  difficult.  The  addition  of  eggs 
that  have  been  beaten  to  a  froth  will  add  air  bubbles.  This 
is  the  method  used  in  making  sponge  cake.  The  water  used 
in  mixing  may  be  replaced  by  soda  water.  This  will  cause 
lightness  by  the  presence  of  carbon  dioxide  bubbles.  This, 
however,  is  not  a  suitable  method  for  the  home,  since  the 
mixing  must  be  carried  out  in  air-tight  vessels,  else  the  gas 
will  escape. 

WEED  CHEMISTRY  —  13  195 


196  CHEMISTRY   IN   THE   HOME 

Chemical  methods  of  leavening  bread.  All  of  these 
mechanical  methods,  while  they  may  be  used,  do  not  satisfy 
the  home  requirements  of  a  quick,  easy  method  of  leavening. 
For  the  home  we  must  resort  to  some  chemical  process.  Re- 
call the  method  of  preparing  carbon  dioxide  by  mixing  a  car- 
bonate and  an  acid.  If  we  can  find  two  such  compounds 
which  can  be  mixed  with  the  flour,  and  which  will  not 
give  any  disagreeable  by-products,  our  problem  is  solved. 
There  are  many  such  combinations  possible.  The  old- 
fashioned  "soda  biscuit"  will  serve  as  an  example.  These 
biscuits  are  made  by  mixing  sour  milk,  which  contains  lactic 
acid,  with  sodium  bicarbonate  (saleratus). 

NaHCO3  +  HC2H5OCO2  ->  NaC2H5OCO2  +  H2O  +  CO2 

This  leaves  nothing  but  sodium  lactate  in  the  biscuit,  and 
there  is  no  objection  to  this.  There  are,  however,  two 
possible  causes  for  failure,  the  addition  of  too  much  or  too 
little  baking  soda.  The  acidity  of  the  sour  milk  will  vary 
within  wide  limits,  and  so  no  receipt  can  tell  just  how  much 
baking  soda  to  use  to  neutralize  it.  If  the  milk  is  unusually 
sour,  acid  will  be  left  and  the  biscuit  will  be  sour.  If  the 
milk  is  not  as  acid  as  usual,  saleratus  will  be  left  over.  Heat 
will  convert  this  into  washing  soda,  and  the  biscuit  will  have 
yellow  streaks  and  taste  soapy  in  places. 

Commercial  baking  powders.  This  difficulty  of  measur- 
ing out  the  exact  amounts  of  acid  and  carbonate  needed  for 
neutralization  applies  to  any  home-made  mixture,  hence  the 
wide  use  of  commercial  baking  powders,  where  the  necessary 
proportions  have  been  determined  by  a  chemist.  There 
are  three  important  varieties  of  baking  powders,  —  cream  of 
tartar,  phosphate,  and  alum  powders. 

Tartrate   baking   powder.     The  acid  taste  of   grapes   is 


BAKING   POWDERS  197 

partly  due  to  the  presence  of  an  acid  tartrate.  When  grapes 
are  pressed,  and  the  juice  allowed  to  stand,  this  acid  tartrate 
is  deposited  as  a  dark  pink  crust  on  the  sides  of  the  vat.  It  is 
called  argols,  and,  when  purified  by  solution  and  recrystalliza- 
tion,  yields  pure  potassium  acid  tartrate,  KHC4H4O6.  This 
is  often  called  cream  of  tartar,  and  is  the  acid  used  in  cream 
of  tartar  powders.  The  carbonate  used  is  sodium  bicarbon- 
ate, XaHCOs,  called  baking  soda.  These  two,  when  mixed 
in  the  proper  proportions,  give  an  excellent  baking  powder. 

KHC4H4O6  +  NaHCO3  ->  KXaC4H4O6  +  H2O  +  CO2 

188         +       84       ->         210          +18    +  44 

If  the  mixed  powder  is  placed  in  a  can  and  kept  for  some 
time,  it  is  difficult  to  avoid  getting  a  little  moisture  in  the 
can  from  the  air.  The  presence  of  this  moisture  causes  the 
acid  and  the  carbonate  to  act  on  each  other,  and  the  powder 
spoils.  To  avoid  this,  20%  of  starch  is  added.  The  starch 
coats  each  particle  of  the  acid  and  carbonate  and  prevents 
their  acting  on  each  other.  At  the  same  time  it  only  adds  a 
little  more  flour  to  the  dough  when  the  powder  is  used,  and 
so  is  not  objectionable. 

An  unscrupulous  manufacturer  may,  however,  use  not 
20  %,  but  50  %  or  more  and  so  make  a  very  inferior  powder, 
and  still  one  that  he  can  advertise  as  perfectly  pure.  The 
amount  of  starch  can  be  readily  determined  by  stirring  a 
teaspoonful  of  the  baking  powder  in  a  glass  of  water.  All  of 
the  materials  are  soluble  except  the  starch,  which  will  sink 
to  the  bottom  of  the  tumbler.  A  comparison  of  two  pow- 
ders in  this  way  will  often  show  that  a  powder  that  is  cheaper 
by  the  pound  is  really  more  expensive  than  a  high-priced 
powder,  owing  to  the  large  amount  of  starch  that  it  contains. 

Occasionally  a  small  amount  of  ammonium  carbonate  is 


198  CHEMISTRY   IN   THE   HOME 

added.  This  volatilizes  in  the  heat  of  the  oven,  and  the 
ammonia  is  driven  off,  while  the  carbon  dioxide  produced 
helps  in  making  the  bread  light. 

The  by-product  of  cream  of  tartar  baking  powder,  potas- 
sium sodium  tartrate  or  Rochelle  salts,  is  left  in  the  bread. 
This  is  a  laxative.  It  is  the  same  product  that  is  formed  by 
seidlitz  powders.  If  large  quantities  of  baking  powder  are 
used  to  make  a  cake  unusually  light,  and  we  eat  an  extra 
piece  of  the  cake  because  it  is  so  good,  the  amount  of  Rochelle 
salts  that  we  take  may  be  more  than  is  desirable.  As  a  rule, 
the  quantity  is  too  slight  to  be  objectionable. 

Phosphate  baking  powder.  The  phosphate  powders  use 
baking  soda  and  calcium  hydrogen  phosphate  (calcium 
superphosphate) . 

CaH4(PO4)2  +  2 NaHCO3  ->  CaHPO4  +  Na2HPO4  +  2  CO2  +  2  H2O 
234        +        168       ->      136      +       142       +    88     +     36 

They  require  a  filler,  just  as  do  all  baking  powders.  The 
substances  left  by  the  reaction  are  not  injurious. 

Alum  baking  powder.  The  alum  powders  contain  baking 
soda  and  alum,  usually  ammonium  alum,  as  that  is  the  cheap- 
est. It  is  a  question  whether  the  residue  left  from  alum  pow- 
ders is  objectionable  or  not.  Many  doctors  say  that  it  is 
decidedly  injurious,  others  that  it  is  harmless.  So  long  as 
there  is  a  question  about  it,  and  there  is  nothing  to  be  gained 
by  their  use,  except  a  small  saving  in  the  cost,  it  is  well  to 
avoid  them. 

(NH4)2A12(SO4)4  +  6  NaHCOs  — >•  2  A1(OH)3  +  3  Na2SO4  +  (NH4)2SO4  +  6  CO2 
475  +        504        —>       157        +      426      +        132        +    264 

Commercial  baking  powders  are  frequently  mixtures  of 
phosphate  and  alum  powders. 

Ratio  of  ingredients  used  in  making  baking  powder. 
The  manufacturer  of  baking  powder  knows  that,  if  he  puts 


BAKING   POWDERS 


199 


cream  of  tartar  and  baking  soda  together,  he  will  make 
baking  powder.  The  question  is,  how  much  of  each  to  use, 
and  for  this  information  he  must  turn  to  the  chemist.  The 
chemist  knows  that  one  molecule  of  baking  soda  will  combine 
with  one  molecule  of  cream  of  tartar,  and  that,  as  a  result, 
Rochelle  salts,  water,  and  carbon  dioxide  will  be  formed. 
This  fact  he  may  express  by  the  following  equation  : 

NaHC03   +  KHC4H4O6   -*  KNaC4H4O6  +   H2O  +  CO2 

baking 
soda 


cream  of 
tartar 


Rochellc 
salts 


.    carbon 
+  dioxide 


Knowing  the  atomic  weights,  he  can  calculate  the  molec- 
ular weights  by  the  following  operation  : 

NaHC03  +  KHC4H406  ->  KNaC4H4O6  +  H2O  +  CO2 


84        + 


188 


210 


+18+44 


SODIUM  BICARBONATE 
Na  =  23 
H  =     1 
C  =  12 

30=3x16=48 
Moi.  wt.  of  NaHCOs          84 

CREAM  OF  TARTAR 

K  =  39 
H  =    1 

4  C  =  4  x  12  =  48 
4H  -  4  x  1  -  4 
6O  =  6  X  16  =  96 

Mol.wt.afKHGH.Q,        188 


ROCHELLE  SALTS 

K  =  39 

Na  =  23 

4  C  =  4  x  12  =  48 

4H  =  4x    1=  4 

6O=6xl6=  96 

Mol.  wt.  of  KNaC4H4O6        210 

WATER 

2H=2xl=2 
O  =    16_ 

Moi.  wt.  of  H2o  18 

CARBON  DIOXIDE 

C  =   12 

2  O  =  2   X  16   ==    32 

Mol.  wt.  of  CO2  44 


Total  weight  used   272     =  Total  weight  obtained  272 


200  CHEMISTRY   IN   THE   HOME 

It  is  apparent  that,  if  the  manufacturer  mixes  84  pounds 
of  sodium  bicarbonate  with  188  pounds  of  potassium  acid 
tartrate,  he  will  have  272  pounds  of  baking  powder  that 
when  used  will  leave  an  excess  of  neither  ingredient.  By 
possessing  this  exact  information  he  not  only  prevents  the 
waste  of  soda  or  cream  of  tartar,  but  produces  a  better  baking 
powder.  He  also  knows  that  84  pounds  of  baking  soda  (so- 
dium acid  carbonate,  or  sodium  bicarbonate)  will  combine  with 
188  pounds  of  cream  of  tartar  (potassium  hydrogen  tartrate, 
or  potassium  acid  tartrate),  to  produce  210  pounds  of  Rochelle 
salts  (potassium  sodium  tartrate),  18  pounds  of  water,  and  44 
pounds  of  carbon  dioxide.  A  simple  proportion  will  then  give 
the  amount  of  each  ingredient  needed  to  produce  any  required 
amount  of  baking  powder.1  Suppose  we  wish  to  manufac- 
ture 100  pounds  of  baking  powder.  Since  84  pounds  of  bak- 
ing soda  will  give  272  pounds  of  baking  powder,  x  pounds  of 
baking  soda  will  give  100  pounds  of  baking  powder.  Or : 

84  :  272  : :  x  :  100.  x  =  30.8+  pounds ;  and  since 

188  pounds  of  cream  of  tartar  are  needed  to  produce  272 
pounds  of  baking  powder,  then  x  pounds  of  cream  of  tartar 
will  produce  100  pounds  of  baking  powder.  Or : 

188  :  272  : :  x  :  100.  x  =  69.1+  pounds.  It  will 

therefore  take  30.8  pounds  of  baking  soda  and  69.1  pounds 
of  cream  of  tartar  to  make  100  pounds  of  baking  powder. 

A  home-made  baking  powder.  A  satisfactory  baking 
powder  can  easily  be  made  at  home  from  the  following : 

Cream  of  tartar,  dried      ...     1  pound 

Cornstarch,  dried \  pound 

Baking  soda \  pound 

1  Baking  powder  usually  contains  some  filler,  as  starch.  This, 
for  the  sake  of  simplicity,  is  omitted  in  the  problem,  as  it  takes  no 
part  in  the  chemical  change. 


BAKING   POWDERS  201 

Divide  the  cornstarch  into  two  equal  parts.  Mix  one  part 
with  the  cream  of  tartar,  and  the  other  part  with  the  baking 
soda.  Then  mix  the  two  together,  place  in  cans  and  in  a 
dry  place.  The  important  things  to  remember  are  that  the 
powders  must  be  dry,  and  that  they  must  be  well  mixed. 
The  cream  of  tartar  and  the  cornstarch  may  be  dried  in  a 
warm  oven.  The  baking  soda,  however,  must  be  used  as 
purchased,  as  heating  it  will  drive  off  some  carbon  dioxide 
and  convert  it  into  washing  soda. 

SUMMARY 

All  baking  powders  liberate  carbon  dioxide  when  mixed  with  the 

dough.     It  is  this  gas  that  makes  the  bread  light. 
Cream    of    tartar    baking   powders    contain    potassium    hydrogen 

tartrate,  sodium  bicarbonate,  and  starch. 
Phosphate  baking  powders  contain  calcium  superphosphate,  sodium 

bicarbonate,  and  starch. 
Alum   baking   powders    contain    alum,  sodium   bicarbonate,  and 

starch. 

Exercises 

1.  Sour  milk  and  baking  soda  will  set  carbon  dioxide  free.     Why 
buy  expensive  baking  powders  to  do  the  same  thing? 

2.  A  mixture  of  marble  and  hydrochloric  acid  will  set  carbon 
dioxide  free.     Why  not  use  this  mixture  instead  of  baking  powder? 

3.  Why  is  baking  soda  instead  of  washing  soda  used  in  baking 
powders? 

4.  Could  carbonated  water  be  used  to  make  bread  light  ? 

5.  Is  a  baking  powder  at  40  cents  a  pound  always  cheaper  than 
one  at  50  cents  a  pound?    Explain. 


CHAPTER  XX 
HYDROCARBONS   AND   DERIVED    COMPOUNDS 

Hydrocarbons.  One  thing  that  simplifies  the  study  of  the 
compounds  of  carbon  is  the  fact  that  many  of  them  can  be 
grouped  into  series.  Thus,  hydrogen  and  carbon  unite  in 
different  proportions  and  form  several  hundred  compounds. 
Many  of  these  occur  in  nature,  while  many  are  the  products 
of  the  laboratory.  They  are  all  called  hydrocarbons.  A 
study  of  a  few  of  them  will  show  us  how  they  may  be  ar- 
ranged in  a  series,  and  how  knowing  the  properties  of  a  few 
of  the  members  of  this  series  will  enable  us  easily  to  remember 
the  properties  of  all. 

The  paraffin  series.  When  rowing,  you  have  doubtless 
pushed  your  oar  into  the  mud  on  the  bottom  of  some  pond, 
and  noticed  that  bubbles  of  gas  arose.  This  gas,  methane, 
CH4,  is  called  marsh  gas,  and  is  formed  when  vegetable 
matter  decays  under  water.  It  is  the  main  constituent  of 
natural  gas. 

In  crude  petroleum  we  find  three  other  gases :  ethane, 
C2H6 ;  propane,  C3H8 ;  and  butane,  C4Hi0.  On  examining 
these  four  formulas,  you  will  see  that,  arranging  them  ac- 
cording to  the  number  of  carbon  atoms  they  contain,  each 
gas  differs  from  the  next  by  the  group  CH2.  We  may  then 
express  all  of  these  formulas  in  one  general  formula,  CnH2n+2. 
If,  then,  we  wish  to  know  the  formula  of  a  hydrocarbon  con- 
taining 16  carbon  atoms,  we  can  find  it  by  multiplying  16  by 

202 


HYDROCARBONS   AND   DERIVED   COMPOUNDS      203 

2  and  then  adding  2.  The  compound  must  then  contain 
34  hydrogen  atoms,  and  its  formula  is  Ci6H34. 

These  hydrocarbons  are  named,  above  the  first  four,  by 
using  as  a  prefix  the  Greek  numeral  that  tells  us  the  number 
of  carbon  atoms  present,  and  following  it  by  the  ending  -ane. 
Thus,  C5Hi2  is  called  pentane.  Reversing  the  process,  if  the 
name  of  the  hydrocarbon  is  octane,  we  know  that  it  is  a  mem- 
ber of  this  series  because  the  name  ends  in  -ane.  It  must 
contain  eight  carbon  atoms  because  of  the  prefix  meaning 
eight,  and  its  formula  must  be  C8Hi8.  This  series  is  known  as 
the  paraffin  series,  and  its  members  have  been  prepared  up 
to  CeoHi22. 

The  properties  of  all  of  the  members  of  the  paraffin  series 
vary  in  a  regular  manner.  Methane  is  a  gas.  With  diffi- 
culty it  can  be  changed  into  a  liquid  having  a  boiling  point  of 
-  164°  C.  Ethane  boils  at  -  89.5°  C.,  propane  at  -  37°  C., 
butane  at  +  1°  C.,  pentane  at  +  35°  C.  Without  studying 
hexane  we  can  then  be  sure  that  it  will  boil  at  about  70°  C. 
Other  properties  vary  in  a  similar  manner,  so  that  the  study 
of  a  few  members  enables  us  to  predict  the  properties  of  all. 

The  ethylene  and  acetylene  series.  There  are  several  such 
series  of  hydrocarbons.  One  starts  with  the  gas  ethylene, 
C2H4.  This  is  the  gas  that  is  present  in  illuminating  gas, 
and  makes  the  flame  luminous.  The  general  formula  of 
this  series  is  CnH2n. 

A  third  series  starts  with  acetylene,  C2H2.  It  is  easily 
made  by  the  action  of  water  on  calcium  carbide : 

2  H20  +  CaC2->C2H2  +  Ca(OH)2 

As  calcium  carbide  can  be  cheaply  made  in  the  electric  furnace 
from  carbon  and  lime,  acetylene  can  be  cheaply  prepared. 

CaO  +  3  C  -*  CO  +  CaC2 


204 


CHEMISTRY   IN   THE    HOME 


Acetylene  is  used  largely  in  the  lamps  of  automobiles,  and 
in  lighting  country  homes  where  ordinary  illuminating  gas 
is  not  available.  Automatic  generators  are  used,  so  arranged 
that  the  gas  is  made  only  as  it  is  burned  (Fig.  71).  They 
require  little  care,  and  give  acetylene,  which  burns  with  an 


tttterlnlet 


Carbide  flofcfer 

FeecfLeve 

__« 

Feec/falve 


GASOMETER 

FIG.  71  —  Automatic  acetylene  generator  and  gas  holder. 

exceedingly  bright  white  light.  The  combustion  of  one 
cubic  foot  of  acetylene  gives  fifteen  times  as  much  light 
as  the  combustion  of  one  cubic  foot  of  illuminating  gas. 
For  this  reason  a  special  burner  is  required  which  per- 
mits only  a  very  small  jet  of  gas  to  escape  to  feed  the 
flame  (Fig.  72) .  An  oxygen  acetylene  flame  gives  an  intense 
heat  and  is  used  in  welding  metals. 


HYDROCARBONS   AND   DERIVED   COMPOUNDS      205 


FIG.  72.-  Acetylene  burner. 


Alcohols.  If  one  of  the  hydrogen 
atoms  of  methane  is  replaced  with 
a  hydroxyl  group,  we  obtain  CH3OH. 
Since  this  is  derived  from  methane, 
its  name  should  suggest  that  gas. 
It  is  called  methyl  alcohol.  An 
alcohol  is  a  hydroxide  derived  from 
a  hydrocarbon.  There  are  hydrox- 
ides derived  from  other  hydrocar- 
bons, as  ethyl  alcohol,  C2H5OH,  and 
butyl  alcohol,  C4H9OH.  Some  alco- 
hols contain  more  than  one  hydroxyl 
group,  as  glycerin,  C3H5(OH)3. 

Aldehydes.  If  we  gently  oxidize 
an  alcohol,  we  obtain  an  aldehyde. 

2  CH3OH  +  02  ->  2  HCHO  +  2  H2O 

This  particular  aldehyde  is  called  methyl  aldehyde.  Its 
trade  name  is  formaldehyde,  or  formalin.  It  is  used  largely 
as  a  disinfectant  and  as  a  preservative.  A  small  amount  is 
sometimes  added  to  milk  to  make  it  keep,  but  this  is  pro- 
hibited by  law,  as  formaldehyde  is  a  poison. 

Organic  acids.     If  the  oxidation  of  an  alcohol  is  carried 
still  further,  we  obtain  an  acid. 

2  HCHO  +  02  ->  2  HCOOH 

The  acid  derived  in  this  way  from  methyl  alcohol  is  formic  acid. 
You  are  familiar  with  one  such  change,  the  oxidation  of  ordi- 
nary alcohol  (ethyl  alcohol),  to  produce  acetic  acid,  or  vinegar. 

C2H5OH  +  02  -*  HC2H302  +  H2O 

Esters.     In  some  ways  the  action  of  an  alcohol  on  an  acid  is 
similar  to  the  action  of  a  metallic  hydroxide  on  an  acid. 


206  CHEMISTRY   IN   THE   HOME 

That  is,  the  organic  hydroxide  will  form  a  salt  with  an  acid, 
just  as  a  metallic  hydroxide  will.  These  organic  salts  are 
called,  esters.  If  sulphuric  acid  is  mixed  with  sodium  acetate, 
acetic  acid  is  set  free  and  sodium  sulphate  is  formed.  If,  now, 
ethyl  hydroxide  (ethyl  alcohol)  is  added,  ethyl  acetate,  a 
liquid  having  an  agreeable  fruity  odor,  results. 


H2S04  +  NaC2H302  -+  NaHSO4 

HC2H3O2  +  C2H5OH  -+  C2H5C2H3O2  +  H2O 

The  odor  and  taste  of  many  flowers  and  fruits  is  due 
largely  to  the  presence  of  these  organic  salts.  Thus,  oil  of 
wintergreen  is  almost  entirely  methyl  salicylate,  mixed  with  a 
small  per  cent  of  ethyl  salicylate.  By  preparing  these  two 
bodies  synthetically  and  mixing  them  in  the  correct  propor- 
tions, an  oil  is  obtained  that  can  hardly  be  distinguished  from 
the  natural  oil  of  wintergreen. 

By  preparing  such  esters  synthetically,  and  mixing  them 
in  the  proper  proportions,  many  flavors  and  perfumes  can 
be  prepared  in  the  laboratory.  Usually,  however,  a  natural 
perfume  is  a  very  complex  mixture,  and  its  aroma  is  due  to  the 
presence  of  small  quantities  of  many  compounds.  To  repro- 
duce it  perfectly  is  therefore  a  difficult  task. 

Fatty  acids.  In  certain  parts  of  Africa,  where  sour  fruits 
are  not  common,  the  natives  regard  large  white  ants  as  a  great 
delicacy.  This  is  because  the  ants  contain  formic  acid, 
which  gives  an  agreeable  acid  taste  to  their  bodies.  This 
formic  acid,  HCHO2,  is  the  first  member  of  the  series  of  the 
organic  fatty  acids,  some  of  the  important  members  of  which 
are  given  in  the  table  on  page  207. 

These  acids  all  contain  the  group  C-O-O-H  (carboxyl 
group),  which  is  characteristic  of  all  organic  acids.  The  first 
members  of  the  group  are  thin  liquids  like  water,  in  which 


HYDROCARBONS   AND   DERIVED   COMPOUNDS      207 


COMMON  ORGANIC  ACIDS 


NAME: 

Formic  acid,  HCHO2, 
Acetic  acid,  HC2H3O2, 
Propionic  acid,  HC3H5O2, 
Butyric  acid,  HC4H7O2, 
Valeric  acid,  HC5H9O2, 
Caproic  acid,  HC6HnO2, 
Caprylic  acid,  HC8Hi5O2, 
Capric  acid,  HCioHigO2, 
Palmitic  acid,  HCi6H3iO2, 
Stearic  acid,  HCi8H35O2, 
Arachidic  acid,  HC20H39O2, 
Medullic  acid,  HC21H4iO2, 
Cerotic  acid,  HC27H53O2, 


FROM: 

Methane,  CH4, 
Ethane,  C2H6, 
Propane,  C3H8, 
Butane,  C4Hi0, 
Pentane,  C5H12 
Hexane,  C6Hi4, 
Octane,  C8Hi8, 
Decane,  CioH22, 


FOUND  IN  : 

Ants,  stinging  nettles. 
Vinegar. 
Wood  distillate. 
Rancid  butter. 
Valerian  root ;  whale  oil. 
Coconut  oil. 
Butter  and  cheese. 
Limburger  cheese. 
Butter  and  tallow. 
Tallow  and  lard. 
Peanut  oil. 

Ox  marrow ;  beef  fat. 
Beeswax. 


they  are  freely  soluble.  They  show  all  of  the  acid  properties 
with  which  we  are  already  familiar.  The  higher  members 
are  still  liquids,  but  become  more  and  more  oily  as  the  number 
of  carbon  atoms  in  the  molecule  increases,  while  the  high- 
est members  are  tasteless  solids,  and  show  only  a  weak 
acidity. 

Some  other  common  fatty  acids,  which  do  not  belong 
in  this  series,  are :  Oleic  acid,  HCi8H33O2 ;  Linoleic  acid, 
HCi8H3iO2 ;  and  Ricissoleic  acid,  HCigHasOa. 

Fats  and  oils.  In  nature  the  higher  fatty  acids  generally 
occur  not  free,  but  combined  with  glycerin,  in  the  form  of 
esters.  These  esters  are  our  ordinary  oils  and  fats.  The 
great  bulk  of  oils  and  fats  is  composed  of  the  glycerides  of 
oleic,  palmitic,  and  stearic  acids.  These  are  called  olein, 
palmitin,  and  stearin.  Olein  is  a  liquid  at  ordinary  tempera- 
tures, palmitin  and  stearin  are  solids.  All  three  are  almost 
tasteless  and  odorless. 

Olive  oil,  as  an  example  of  an  oil,  consists  mainly  of  olein 


208  CHEMISTRY   IN   THE   HOME 

and  palmitin.  Lard,  as  an  example  of  a  fat,  has  the  same 
composition.  Lard,  however,  is  solid  because  it  contains  a 
larger  percentage  of  palmitin  than  does  olive  oil.  Beef  tallow 
is  mainly  stearin,  and  is  hard.  The  consistency  of  a  fat 
depends  upon  the  proportions  of  the  olein,  stearin,  and 
palmitin  that  it  contains. 

The  differences  in  the  flavors  of  fats  and  oils  are  due  to 
small  amounts  of  other  compounds  present.  Fats  and  oils 
cannot  be  distilled,  as,  when  heated  much  above  their  melting 
point,  they  decompose,  giving  off  an  acrid  smoke.  The 
various  fats  and  oils  are  insoluble  in  water,  but  are  easily 
dissolved  in  such  organic  solvents  as  gasoline,  ether,  and  oil 
of  turpentine.  Carbon  tetrachloride,  CC14,  is  largely  used 
as  a  fat  solvent  under  the  trade  name  of  Carbona. 

The  formulas  of  the  common  fats  are  :  Palmitin, 
Olein,  C3H5(Ci8HjA)s  ;  Stearin,  C3H5 


Hydrolysis.  When  a  fat  becomes  rancid,  it  is  due  to  the 
separation  of  the  glycerin  and  the  fatty  acid  radical,  setting 
free  the  fatty  acid  itself.  Thus,  the  glyceryl  butrate  con- 
tained in  butter  is  easily  decomposed  into  glycerin  and 
butyric  acid.  Butyric  acid  has  a  very  disagreeable  taste 
and  odor,  and  we  say  that  the  butter  has  become  strong. 
This  change  is  called  hydrolysis,  because  water  is  taken  up. 

C3H5(C4H702)3  +  3  H20  -^  C3H5(OH)3  +  3  HC^A 

glyceryl  +     water  —  >.        glycerin         +         butyric 

butrate  acid 

Benzol.  Benzol,  C6H6,  is  obtained  from  coal  tar  by  distil- 
lation. It  is  the  starting  point  for  thousands  of  synthetic 
compounds,  many  of  which  are  used  in  medicine.  Benzol  is 
a  colorless,  volatile  liquid.  It  burns  with  a  smoky  flame,  and 
is  one  of  the  illuminants  in  gas.  It  is  much  used  as  a  solvent 


HYDROCARBONS   AND    DERIVED   COMPOUNDS      209 

for  sulphur,  phosphorus,  oils,  and  rubber.  As  it  readily 
dissolves  grease,  it  is  used  to  "  dry  clean  "  clothes. 

Nitrobenzol.  Nitrobenzol,  C6H5NO2,  is  made  by  the 
action  of  nitric  acid  upon  benzol.  It  is  a  heavy,  oily  liquid, 
having  the  odor  of  bitter  almonds.  It  is  used  as  a  scent  in 
soap,  under  the  name  of  oil  of  mirbane,  or  artificial  oil  of 
bitter  almonds. 

Aniline.  Aniline,  C6H5NH2,  is  made  from  nitrobenzol  by 
reducing  it  with  nascent  hydrogen.  Hydrogen,  produced 
by  the  action  of  zinc  on  hydrochloric  acid,  at  the  instant  of 
its  liberation,  is  very  energetic.  It  is  said  to  be  nascent.  Ani- 
line is  a  volatile,  colorless  liquid,  which  unites  directly  with 
acids  to  form  salts,  as  aniline  hydrochlorate,  CeH^Xt^HCl. 
Toluidin,  C6H4CH3NH2,  resembles  aniline.  These  two  com- 
pounds are  interesting  to  us,  because  their  mixture,  when 
oxidized,  yields  the  various  colors  known  as  aniline  dyes. 
A  slight  change  in  the  composition  of  these  dyes  changes 
the  color  very  materially. 

Carbolic  acid.  Phenol,  carbolic  acid,  C6H5OH,  is  chemi- 
cally not  an  acid  at  all.  It  has,  however,  a  corrosive  action 
on  flesh,  whence  its  popular  name  of  acid.  It  is  found  in  coal 
tar,  and  is  separated  from  it  by  distillation.  Pure  phenol  is  a 
colorless,  crystalline  solid,  soluble  in  20  parts  of  water  at 
ordinary  temperatures.  Its  solution  is  a  powerful  antiseptic, 
and  is  used  as  a  disinfectant.  It  is  poisonous,  and  should 
be  used  with  care. 

Some  important  benzol  derivatives.  Acetanilide,  some- 
times named  antifebrine,  used  as  a  sedative  and  for  fevers; 
phenacetin,  used  in  headache  powders;  naphthalene,  the 
white  crystal  sold  as  "  moth  balls  ";  and  creosote,  used  as  a 
wood  preservative  and  a  medicine,  are  a  few  of  the  benzol 
series  compounds  that  are  of  importance  to  us. 


210  CHEMISTRY   IN   THE   HOME 

SUMMARY 

A  hydrocarbon  is  a  compound  containing  hydrogen  and  carbon. 

An  alcohol  is  an  organic  hydroxide. 

An  aldehyde  is  the  product  of  the  partial  oxidation  of  an  alcohol, 

and  always  contains  the  group  C-O-H. 
An  organic  acid  is  the  product  of  the  oxidation  of  an  alcohol,  and 

contains  the  carboxyl  group  C-O-O-H. 
An  ester  is  an  organic  salt. 

A  fat  or  oil  is  a  glyceride  of  oleic,  palmitic,  or  stearic  acid. 
Benzol  is  a  hydrocarbon  obtained  from  coal  tar.      Nitrobenzol, 

aniline,  and  thousands  of  other  compounds  are  made  from  it. 

Exercises 

1.  How  would  you  remove  a  grease  spot  from  a  suit? 

2.  Rancid  butter,  when  washed  with  water,  becomes  edible. 
Why? 

3.  How  could  you  make  ethyl  nitrate? 

4.  Sodium  oleate  is  soluble  in  water.     If  sulphuric  acid  is  added 
to  the  solution,  a  white  insoluble  solid  is  set  free.     What  is  it? 
Write  the  equation. 

5.  How  could  you  convert  an  aldehyde  into  an  acid? 


CHAPTER  XXI 
OILS,   FATS,   AND    SOAP 

THERE  are  so  many  thousands  of  organic  compounds  that 
no  one  man  knows  all  their  properties  and  uses.  A  few  of 
them  though  are  used  so  largely  in  our  daily  life  that  we 
should  know  something  of  their  preparation  and  uses. 
Among  the  most  important  of  these  are  the  oils  and  fats, 
used  so  extensively  as  foods. 

Methods  of  extracting  oils.  There  are  a  number  of  general 
methods  used  to  extract  oils.  One  that  is  largely  used  is  press- 
ing, or  expressing,  as  it  is  generally  called.  The  material  is 
placed  in  bags,  and  pressed,  gently  at  first,  which  yields  the 
best  oil,  and  then  more  forcibly,  which  yields  an  oil  of  a 
somewhat  lower  grade.  Olive  oil  is  obtained  by  this  process. 

Volatile  oils,  as  the  oil  of  cloves,  are  often  extracted  by 
placing  the  ground  material  in  a  still,  and  then  passing  live 
steam  into  it  under  pressure.  The  volatile  oil  is  carried 
over  with  the  steam,  and,  condensing  with  it,  sinks  to  the 
bottom  of  the  receiver.  Minute  traces  of  essential  oils  may 
be  extracted  by  this  process.  Thus  it  takes  4000  pounds  of 
rose  leaves  to  furnish  one  pound  of  the  pure  oil  of  rose  by 
steam  distillation. 

The  oil  obtained  by  distillation  from  flowers  does  not 
always  have  the  exact  odor  of  the  flower,  for  the  flower  odor 
is  a  blend  of  the  odor  of  many  substances,  not  all  of  which  are 
volatilized  with  the  steam.  Then,  too,  the  heat  of  the  steam 

WEED   CHEMISTRY 14  211 


212  CHEMISTRY   IN   THE    HOME 

destroys  some  of  the  more  delicate  odors.  To  avoid  these 
difficulties,  some  of  the  more  delicate  flower  odors  are  ob- 
tained by  the  enfleurage  process.  A  neutral,  odorless  fat 


a.    Distillation  of  volatile  oils  from  geraniums. 


6.    Sorting  roses  for  extraction  of  oils  by  the  enfleurage  process. 
FIG.  73.  —  Preparation  of  essential  oils. 

is  spread  on  glass  plates,  and  the  flowers  strewn  on  it  (Fig. 
74).  The  fat  absorbs  the  odor,  and,  when  the  flowers  are 
exhausted,  they  are  replaced  by  fresh  ones.  This  is  repeated 


OILS,    FATS,    AND    SOAP 


213 


until  the  fat  has  become  saturated  with  the  perfume  of  the 
flower.  From  this  fat  the  odor  is  extracted  with  alcohol. 

Some  oils  are  ob- 
tained by  the  use  of 
solvents.  The  ground 
material  is  placed  in 
closed  vessels  and 
treated  with  an  oil 
solvent,  as  benzine. 
The  solution  obtained  ,-, 

FIG.  74. —  Trays  used  in  extraction  of  volatile 
is  then  distilled  to  re-  oils  by  the  enfleurage  process. 

cover  the  solvent.  The  yield  is  larger  than  that  obtained 
by  pressing,  but  the  apparatus  used  is  costly,  and  the  press 
cake  obtained  cannot  be  used  as  a  cattle  food.  The  proc- 
ess is  therefore  used  mainly  to  obtain  the  essential  oils 
from  flowers,  where  the  material  to  be  handled  is  not  large 
in  bulk,  and  the  product  obtained  is  high  in  price. 

Fats  and  oils  classified.  There  is  no  chemical  difference 
between  fats  and  oils.  If  they  are  liquid  at  ordinary  tem- 
peratures, we  call  them  oils ;  if  solid,  fats.  Even  this  rule  is 
not  of  universal  application,  for  palm  oil  is  a  solid.  Waxes, 
however,  belong  to  a  different  class  of  compounds.  They 
are  as  a  rule  fatty  acid  radicals  united  with  an  alcohol  of  some 
other  than  the  glycerin  series.  Chemically,  the  paraffin 
oils  are  not  oils  at  all,  but  hydrocarbons. 

For  our  purpose,  fats  and  oils  may  be  classified  as  drying 
oils,  such  as  linseed  oil,  which,  exposed  to  air,  oxidize  and 
become  solid;  semi-drying  oils,  which  partially  oxidize; 
non-drying  oils,  which  do  not  change  on  exposure  to  the  air, 
as  olive  oil;  and  volatile  oils,  such  as  oil  of  cloves,  that 
readily  evaporate.  The  first  three  classes  are  sometimes 
called  fixed  oils,  because  they  are  non- volatile. 


214 


CHEMISTRY   IN   THE    HOME 


Linseed  oil.  Linseed  oil  is  obtained  by  pressure  from  the 
ground  seeds  of  the  flax  plant.  It  is  light  yellow  in  color. 
Its  drying  properties  make  it  valuable  in  paints  and  varnish. 
Linoleum  is  made  by  mixing  ground  cork  with  linseed  oil. 
The  oil  dries,  that  is,  oxidizes  and  becomes  a  solid,  thus  bind- 
ing the  particles  of  cork  together.  To  hasten  this  oxidation, 
the  oil  is  heated  with  salts  of  manganese  or  lead.  These 
compounds  are  known  as  driers.  The  oxidation  of  linseed 
oil,  and  other  drying  oils,  generates  heat,  and  is  often  a 
cause  of  spontaneous  combustion. 

Cottonseed  oil.  Cottonseed  oil  is  one  of  the  semi-drying 
oils.  It  is  obtained  by  expression  from  the  cotton  seed  left 


FIG.  75.  —  A  filter  press. 

from  ginning  cotton.  The  press  cake  left  after  the  oil  is 
pressed  out  is  used  as  a  cattle  food.  The  oil  at  first  is  almost 
black.  To  purify  it,  the  oil  is  agitated  with  a  small  amount 
of  dilute  sodium  hydroxide  solution.  This  removes  the 
color  and  free  fatty  acids.  On  standing,  the  pure  yellow  oil 
separates,  is  drawn  off,  and  washed  with  water. 

Cottonseed  oil  is  used  in  the  manufacture  of  soap,  and 


OILS,   FATS,   AND   SOAP  215 

for  edible  purposes.  The  "  salad  oil  "  of  the  grocer  is  likely  to 
be  cottonseed  oil.  On  cooling  the  oil,  stearin  separates  as  a 
light  yellow  solid  of  the  consistency  of  butter.  This  is  filtered 
out  and  used  largely  in  making  lard  and  butter  substitutes. 

Sesame  oil.  Sesame  oil  is  obtained  from  Sesamum  orien- 
tale,  grown  in  India,  China,  and  West  Africa.  It  has  a  pleas- 
ant taste,  and  is  used  to  some  extent  in  cooking.  It  is 
cheaper  than  olive  oil,  and  can  be  used  instead  of  it  for 
many  purposes  in  the  household.  It  deserves  a  more  ex- 
tended use. 

Peanut  oil.  Peanut  oil  is  obtained  from  the  shelled  nut  of 
the  common  peanut  by  pressure.  The  cold  pressed  oil  has  a 
pleasant  flavor  and  is  used  as  a  salad  oil.  A  second  quality 
obtained  by  hot  pressing  is  darker  in  color,  and  is  used  in  the 
manufacture  of  soap.  Peanut  oil  is  a  typical  non-drying 
oil,  that  is,  it  does  not  become  thick  because  of  oxidation  on 
exposure  to  the  air. 

Olive  oil.  Olive  oil,  used  so  extensively  as  an  edible  oil, 
is  obtained  by  crushing  and  pressing  ripe  olives.  The  ripe 
olive  is  dark  in  color,  rich  in  oil,  and  very  different  from  the 
bottled  olives  with  which  you  are  familiar.  The  first  gentle 
pressing  yields  the  "  virgin  oil,"  which  is  the  best  grade  of 
table  oil.  The  pulp  is  then  treated  with  water  and  pressed 
again.  This  gives  a  slightly  inferior  oil,  which  is  used  in 
cooking  and  for  salads.  A  final  treatment  with  hot  water 
and  pressure  yields  an  oil  suitable  only  for  soap  making.  It 
is  from  this  oil  that  castile  soap  is  made.  Olive  oil  is  a  non- 
drying  oil. 

Other  vegetable  fats.  Several  other  vegetable  fats  are  of 
importance.  Palm  oil,  obtained  from  the  fruit  of  palm  trees, 
and  coconut  oil  obtained  from  the  coconut,  are  largely  used 
in  making  soap.  Cocoa  butter  is  the  fat  pressed  from 


216  CHEMISTRY   IN   THE    HOME 

chocolate  in  the  manufacture  of  cocoa,  and  is  used  in  toilet 
preparations,  ointments,  and  in  confectionery. 

How  animal  fats  are  extracted.  Animal  oils  arid  fats  are 
"  rendered."  The  fat  is  cut  into  small  pieces  and  thrown 
into  a  kettle,  where  it  is  heated  with  live  steam.  After  the 
fat  has  melted,  the  content  of  the  kettle  is  filtered  to  remove 
the  animal  membranes,  and  the  liquid  allowed  to  stand.  The 
oil  rises  and  is  removed.  The  watery  remainder  is  used  with 
a  second  portion  of  fat.  Beef  tallow,  mutton  tallow,  and 
lard  are  obtained  in  this  way. 

Butter  and  lard  substitutes.  Butter  substitutes,  called 
butterine  or  oleomargarine,  are  made  by  rendering  beef  fat  at 
a  low  temperature.  This  frees  it  from  the  animal  membranes. 
The  clear  fat  is  then  cooled  and  kept  for  some  days  at  a 
temperature  of  about  80°  F.  in  order  that  the  stearin  con- 
tained in  it  may  separate.  The  fat  is  then  placed  in  bags, 
and  subjected  to  a  heavy  pressure  to  separate  the  stearin 
from  the  oleo  oil.  This  oleo  oil  that  runs  out  from  the  bags  is 
a  clear,  tasteless,  light  yellow  fluid,  which  solidifies,  on  cooling, 
to  a  crumbly  mass.  White  stearin  is  left  in  the  bags,  and  is 
used  to  make  candles. 

This  oleo  oil  would  not  be  an  acceptable  substitute  for 
butter,  as  it  would  lack  the  butter  flavor.  This  flavor  is 
imparted  to  it  by  churning  it  with  milk,  at  a  temperature 
that  will  keep  the  oleo  oil  melted.  This  adds  a  small  amount 
of  butter  to  the  fat,  and  gives  it  an  agreeable  flavor.  To 
make  the  flavor  of  the  butterine  more  like  that  of  butter, 
small  amounts  of  propionic,  butyric,  and  capric  acids  are 
sometimes  added.  Cottonseed  oil  or  cottonseed  stearin 
are  also  often  added. 

To  give  it  a  grain  similar  to  butter,  the  mass  is  then  cooled 
suddenly  by  running  it  into  ice  water.  It  is  then  worked 


OILS,   FATS,   AND   SOAP  217 

to  free  it  from  water;  it  is  salted  and  colored  in  the  same 
way  that  ordinary  butter  is.  As  in  winter  the  product 
would  be  too  hard  to  resemble  butter,  some  soft  fat,  as  cot- 
tonseed oil,  is  added. 

Butterine  has  an  advantage  over  butter  in  that  it  is  much 
cheaper,  and  keeps  better,  as  it  contains  less  of  the  easily 
decomposed  glycerides.  It  is  probably  somewhat  less 
digestible  than  pure  butter,  but  not  enough  so  as  to  render 
its  use  objectionable.  To  sell  oleo  as  butter  is  of  course  a 
fraud,  but  to  sell  it  on  its  own  merits,  as  a  cheap  butter  sub- 
stitute, is  not  objectionable. 

Mixtures  of  beef  and  cottonseed  oil  are  largely  used  in 
cooking  under  such  names  as  Cottolene.  The  beef  fat  in 
this  is  expensive,  and  chemists  have  lately  found  a  way  to 
add  hydrogen  to  cottonseed  oil,  thus  converting  it  into  a 
hard  solid.  This  is  used  in  Crisco  and  other  lard  substi- 
tutes instead  of  the  more  expensive  beef  fat. 

Manufacture  of  oilcloth.  The  drying  qualities  of  linseed 
oil  are  taken  advantage  of  in  the  manufacture  of  oilcloth  and 
linoleum.  To  make  oilcloth,  burlap  is  first  sized,  so  as  to 
fill  up  the  pores.  It  is  then  heated,  to  dry  it.  This  pre- 
pared cloth  is  then  thickly  covered  with  red  lead  paint,  which 
is  linseed  oil  mixed  with  red  lead.  This  painting  is  repeated 
five  times,  the  cloth  being  heated  after  each  painting  to 
hasten  the  drying  of  the  oil.  The  surface  is  then  rubbed 
with  pumice,  to  make  it  even.  The  design  is  printed  on  the 
surface,  using  a  special  form  of  printing  press.  The  cloth 
is  again  heated,  and  then  taken  to  the  varnishing  machine. 
Here  the  glossy  finish  is  given  it  by  flowing  on  it  a  coat  of 
varnish.  A  final  heating  to  dry  the  varnish  finishes  the 
operations. 

If  a  thin  table  or  shelf  oilcloth  is  to  be  made,  the  process  is 


218  CHEMISTRY   IN   THE   HOME 

much  the  same.  Cotton  sheeting  is  used  as  the  foundation, 
and  this  is  coated  with  a  mixture  of  linseed  oil  and  china  clay. 
This  may  be  colored  to  give  any  desired  tint.  The  design  is 
printed  on  the  finished  oilcloth  in  a  cylinder  press,  similar 
to  those  used  in  calico  printing.  It  is  then  varnished,  heated 
for  24  hours  to  dry  it,  and  is  then  ready  for  use. 

Manufacture  of  linoleum.  Linoleum  is  made  by  boiling 
linseed  oil  in  large  kettles,  with  the  addition  of  driers,  until 
it  becomes  thick.  Canvas  sheets  are  then  dipped  in  the  oil, 
and  hung  up.  The  sheets  are  flooded  with  oil  twice  a  day, 
and,  being  kept  in  a  room  the  temperature  of  which  is  165°  F., 
the  oil  rapidly  hardens. 

In  two  or  three  weeks  the  mass  of  hardened  oil  has  be- 
come so  thick  that  the  canvas  sheet  resembles  a  thin  board. 
The  "  skins  "  are  now  cut  down,  and  ground  up  into  flakes. 
These  flakes  are  mixed  with  powdered  cork,  and  wood  pulp, 
and  any  color  desired  is  added.  The  mass  is  then  passed 
between  rollers,  which  press  it  into  a  sheet  18  inches  wide  by 
|  inch  thick.  These  sheets  have  the  consistency  of  soft 
putty.  Dies  now  cut  these  differently  colored  sheets  into 
blocks.  These  are  laid  on  a  burlap  covered  with  red  lead 
paint,  so  as  to  form  any  desired  design.  A  pressure  of  3000 
pounds  to  the  square  inch  is  then  applied,  using  a  hydraulic 
press.  This  consolidates  the  material  into  one  solid  mass. 
To  complete  the  drying  of  the  oil,  the  linoleum  is  then  heated 
to  145°  F.  for  from  four  to  five  weeks.  Varnishing  completes 
the  process,  and  the  linoleum  is  ready  for  market. 

This  is  the  best  grade,  called  inlaid  linoleum.  As  the  colors 
go  through  from  front  to  back,  they  cannot  wear  off,  as  they 
do  in  oilcloth.  A  cheaper  grade  of  linoleum  is  made  by 
printing  the  design  on  the  surface,  instead  of  inlaying  it. 
Cork  carpet  is  linoleum  made  of  an  extra  thickness,  and  only 


OILS,   FATS,   AND   SOAP  219 

powdered  cork  is  used  as  a  filler.     It  is  expensive,  but  lasts 
almost  indefinitely. 

Saponification  explained.  When  any  of  the  common  fats 
or  oils,  which  are  all  glycerides  of  fatty  acids,  are  treated 
with  a  metallic  hydroxide,  a  change  called  saponification  takes 
place.  The  fatty  acid  radical  of  the  fat  combines  with  the 
metal,  while  the  glyceryl  radical  combines  with  the  hydroxyl, 
producing  glycerin. 


C3H5(C17H35CO2)3  +  3  NaOH  ->  C3H6(OH)3  +  3 

glyceryl  +     sodium   —  >•     glycerin      +  sodium 

stearate  hydroxide  stearate 

If  we  use  sodium  or  potassium  hydroxides,  the  resulting  salt 
is  soluble  in  water  and  is  called  soap.  By  using  lead  or  zinc 
hydroxides,  we  can  form  lead  soaps  or  zinc  soaps,  but,  since 
these  are  insoluble,  they  are  of  no  value  as  soaps.  Zinc 
oleate  is  used  as  the  basis  for  zinc  ointment. 

Manufacture  of  soap.  Common  laundry  soap  is  made 
largely  from  animal  fats.  The  tallow  or  grease  used  comes 
to  the  soap  factory  in  large  iron  or  wood  casks.  Live  steam  is 
used  to  melt  the  fat,  which  is  then  placed  in  large  iron  vats 
holding  several  tons.  Here  sodium  hydroxide  is  added,  and 
the  mass  heated  by  steam  coils.  The  boiling  is  continued 
until  saponification  occurs. 

A  salt  solution  is  then  added.  As  soap  is  insoluble  in 
brine,  the  contents  of  the  vat  separate  into  two  layers,  an 
upper  layer  of  soap,  and  a  lower  layer  of  brine  mixed  with 
glycerin  and  some  impurities,  TRe  lower  layer  is  drawn  off 
and  the  glycerin  recovered  from  it.  This  is  the  source  of 
practically  all  of  the  glycerin  of  commerce.  The  soap  re- 
mains in  the  vat.  The  change  is  a  slow  one,  the  whole 
process  taking  about  forty-eight  hours. 

Soda  lye  is  then  again  added,  and  live  steam  introduced 


220 


CHEMISTRY   IN   THE   HOME 


until  the  mass  is  once  more  boiling.  In  laundry  soaps  rosin 
is  now  introduced.  This  makes  the  soap  lather  well,  and 
cheapens  the  product. 

In  good  grades  of  toilet  soap  no  rosin  is  used.  About  half 
as  much  rosin  is  added  as  fat  was  used.  Rosin  soap  is  not 
as  good  a  detergent  as  a  fat  soap,  but  its  cost  is  much  less. 
Sufficient  sodium  hydroxide  must  be  used  to  saponify  the 
rosin,  as  well  as  to  complete  the  saponification  of  the  fats. 
When  the  saponification  is  complete,  brine  is  again  added, 
and  the  soap  allowed  to  stand  until  it  has  again  separated. 
The  lower  layer  is  then  drawn  off.  This  requires  about 
twenty-four  hours. 

A  third  charge  of  strong  sodium  hydroxide  is  then  added, 
and  the  mass  heated  with  steam.  This  is  to  insure  the 
saponification  of  all  of  the  fat  and  rosin.  This  is  called  the 
"  strength  change,"  and  requires  twenty-four  hours.  The 
soap  is  now  finished,  but  it  still  contains  some  lye  and 


FIG.  76.  —  A  crutcher.     a.  External  view.     b.  Section. 


OILS,   FATS,   AND   SOAP 


221 


impurities.     These  are  removed  by  boiling  with  water  until 
the  soap  loses  its  granularity,  and  becomes  a  smooth  mass. 

The  contents  of  the  vat  are  now  allowed  to  remain  undis- 
turbed for  two  days,  when  three  layers  form.  The  upper 
is  the  pure  soap.  The  next  is  a  dark  layer  of  soap  mixed 
with  impurities.  This  is  allowed  to  remain  in  the  vat  until 
enough  has  accumulated  to  make  it  worth  while  to  bleach  it. 
It  is  sold  as  a  low  grade  soap.  The  bottom  layer  is  lye,  which 
is  drawn  off  and  used  again. 

The  soap  is  run  into  a  mixing  machine  called  a  crutcher, 
where  sodium  silicate,  borax,  or  sodium  carbonate,  is  added 
(Fig.  76).  Sodium  silicate 
is  added  to  make  the  soap 
hard,  and  prevent  its 
wasting  away  too  quickly. 
The  soap  is  then  run 
into  large  wooden  frames, 
where  it  solidifies.  It  is 
cut  into  cakes,  and  after 
these  have  dried  a  little, 
they  are  stamped  with  the 
design  of  the  manufac- 
turer, wrapped,  and  sold. 

Manufacture  of  toilet 
soap.  In  making  toilet 
soap,  the  soap,  after  cool- 
ing in  the  frames,  is  cut 
into  chips,  dried,  and  run 
through  a  second  mixing 
machine  called  a  mill. 
Here  the  color  and  per- 
fume are  added.  To  pro-  FIG.  77.  —  Soap  stamping  machine. 


CHEMISTRY   IN   THE    HOME 

duce  the  medicinal  soaps,  antiseptics,  creosote,  carbolic  acid, 
and  other  products  are  added  to  the  soap  in  the  mill.  The 
soap  is  then  pressed  into  cakes  and  stamped  (Fig.  77). 

Potassium  soaps  lather  more  freely  than  sodium  soaps. 
Shaving  soaps  are  therefore  potassium  soaps.  A  little  potas- 
sium bicarbonate  is  also  often  added.  In  making  soft  soap, 
potassium  hydroxide  is  used  instead  of  sodium  hydroxide. 

Soap  fats.  The  fats  used  depend  on  the  product  desired. 
The  cheaper  fats  are  used  in  laundry  soaps,  while  the  more 
expensive  are  used  in  toilet  soaps.  Floating  soaps  are  made 
by  beating  air  into  the  soap  while  it  is  soft.  They  are  no 
purer  than  other  kinds. 

Water  in  soap.  It  is  to  the  advantage  of  the  manufacturer 
to  sell  soap  containing  a  large  quantity  of  water.  A  seem- 
ingly dry  coconut  oil  soap  may  contain  60%  of  water.  Soap 
will  last  longer,  if  allowed  to  stand,  unwrapped,  in  the 
air  after  buying  it,  as  this  allows  some  of  the  water  to 
evaporate.  The  soap  is  then  harder  and  does  not  waste 
away  so  quickly.  Common  laundry  soap  will  lose  25%  of 
its  weight. 

Soap  powders.  Soap  powders  are  made  by  grinding  dry 
soap  to  a  powder,  and  adding  sodium  carbonate  or  borax. 
If  you  will  weigh  the  contents  of  a  box  of  any  of  the  soap 
powders,  and  compare  its  cost  with  the  cost  of  an  equal 
amount  of  soap  and  sodium  carbonate,  you  will  find  that  they 
are  very  expensive.  You  can  make  an  equivalent  preparation 
at  home  at  much  less  cost. 

Scouring  soaps.  If  an  abrasive  is  added  to  the  soap,  we 
have  a  scouring  soap,  as  the  familiar  Sapolio.  These  scouring 
soaps  are  usually  dried  in  molds,  as  they  are  difficult  to  cut. 
Ground  quartz,  feldspar,  or  pumice  are  some  of  the  abrasives 
added.  They  also  often  contain  a  little  sodium  carbonate. 


OILS,   FATS,  AND    SOAP  223 

Cold  process  soap.  It  is  not  necessary  to  boil  fat  to  sapon- 
ify it.  In  the  cold  process  of  making  soap,  the  fat  and  sodium 
hydroxide  are  mixed  together  and  allowed  to  stand.  If 
alcohol  is  used  instead  of  water  a  liquid  soap  is  obtained. 
Transparent  soaps  are  made  by  dissolving  soap  in  alcohol 
and  distilling  off  the  alcohol.  This  leaves  the  soap  as  a 
transparent  jelly. 

Soaps  to  be  avoided.  In  buying  soap,  do  not  buy  a 
cheap,  soft,  highly  colored,  and  scented  variety.  The 
color  and  scent  were  added  for  the  purpose  of  concealing 
poor  materials.  A  toilet  soap  should  be  neutral,  as  other- 
wise it  damages  the  skin. 

Action  of  soap  on  hard  water.  When  soap  is  used  with 
hard  water,  a  white  precipitate  forms.  This  is  lime  soap, 
and  represents  a  considerable  waste.  To  avoid  this,  the 
water  should  be  softened  before  the  soap  is  used.  This 
may  be  done  by  boiling,  in  the  case  of  temporary  hard 
waters  :  1 

CaH2(CO3)2  +  heat  ->  CaCO3  1  +  H2O  +  CO2 
or,  by  the  addition  of  washing  soda  to  permanently  hard 
waters  : 

CaSO4  +  Na^COs  ->  CaCO3  1 


SUMMARY 

Fats  and  oils  are  obtained  by  expressing,  by  enfleurage,  by  dis- 
solving in  an  oil  solvent,  and  by  distillation  with  steam. 

Drying  oils,  as  linseed  oil,  oxidize  on  exposure  to  the  air  and  become 
solid. 

Non-drying  oils,  as  olive  oil,  do  not  change  on  exposure  to  the  air. 

Semi-drying  oils,  as  cottonseed  oil,  thicken  on  exposure  to  the  air. 

1  Temporary  hard  water  contains  soluble  calcium  acid  carbonate 
which  is  decomposed  when  the  water  is  boiled.  Permanent  hard 
water  contains  calcium  sulphate  which  is  not  affected  by  boiling. 


224  CHEMISTRY   IN   THE   HOME 

Fixed  oils,  as  corn  oil,  are  no n- volatile. 

Volatile  oils,  as  oil  of  cloves,  readily  evaporate. 

Oleomargarine,  or  butterine,  is  made  from  beef  fat  mixed  with  cot- 
tonseed oil.  A  small  amount  of  real  butter  is  mixed  with  it  to 
give  it  a  butter  flavor.  It  is  a  cheap,  desirable,  butter  sub- 
stitute. 

Linoleum  and  oilcloth  are  cloths  covered  with  a  very  thick  layer  of 
oil  or  paint. 

Soap  is  a  sodium  or  potassium  salt  of  a  fatty  acid. 

Soft  soaps  are  potassium  soaps. 

Hard  soaps  are  sodium  soaps. 

Liquid  soap  is  a  solution  of  soap  in  weak  alcohol. 

Scouring  soaps  contain  some  abrasive,  as  powdered  feldspar. 

Exercises 

1.  How  would  you  tell  to  which  class  of  oils  peanut  oil  belongs? 

2.  Would  you  be  willing  to  use  butterine  at  home?     Explain. 

3.  How  could  you  prepare  oil  of  cinnamon  at  home? 

4.  How  could  you  clean  a  greasy  waist? 

6.    Could  linseed  oil  be  used  to  adulterate  olive  oil?     Explain. 

6.  Why  is  oil  of  rose  so  expensive  ? 

7.  How  could  rancid  butter  be  made  fit  for  use  ?    Is  this  ren- 
ovated butter  worth  as  much  as  fresh  butter  ? 

8.  How  could  you  distinguish  betweeen  a  soft  and  a  hard  water  ? 


CHAPTER  XXII 
CARBOHYDRATES 

Carbohydrates  defined.  Nature  is  the  great  master 
chemist  of  the  world,  and  one  of  her  most  marvelous  doings 
is  seen  in  the  ease  with  which  she  builds  up  complex  organic 
compounds  from  the  simplest  materials,  as  in  the  produc- 
tion of  starch  by  green  plants.  The  chlorophyll  cells  of 
plants  having  green  leaves  are  able,  under  the  influence  of 
sunlight,  to  cause  carbon  dioxide  and  water  to  combine, 
forming  an  organic  compound  and  setting  free  oxygen. 
Just  how  the  plant  does  this,  we  do  not  yet  know.  The 
equation  below  represents  only  the  end  products;  of  the 
intermediate  steps  we  are  not  sure. 

6  CO2  +  5  H2O  ->  C6H1005  +  6  O2 

You  will  notice  that  in  the  formula  of  the  compound 
formed,  called  starch,  hydrogen  and  oxygen  occur  in  the 
proportion  in  which  they  are  present  in  water,  and  that 
there  are  six  atoms  of  carbon.  Compounds  of  which  this 
is  true  are  called  carbohydrates.  In  them  you  will  always 
find  oxygen  and  hydrogen  present  in  the  proportion  of  1 :  2, 
and  carbon  present  as  six  atoms,  or  a  multiple  of  six.  These 
carbohydrates  are  very  important  compounds  for  our  study, 
as  they  include  the  sugars,  starch,  and  cellulose.  These 
compounds  are  of  especial  interest  in  the  home. 

Cane  sugar.  Cane  sugar,  or  sucrose,  C^^On,  is  found 
in  many  plants,  but  in  most  of  them  it  occurs  in  too  small 

225 


226 


CHEMISTRY   IN   THE    HOME 


quantities  to  pay  for  extracting.  All  that  is  of  importance 
commercially  comes  from  sugar  cane,  sugar  beet,  and  sugar 
maple. 

Sugar  cane  is  a  large,  jointed  grass,  somewhat  like  corn, 
numerous  varieties  of  which  are  grown  in  tropical  and  sub- 
tropical regions  of  the  earth,  as  Cuba,  Louisiana,  and  Texas 
(Fig.  78).  The  stalk  of  sugar  cane  contains  from  12%  to 


FIG.  78.  —  Growing  sugar  cane. 

20%  of  cane  sugar.  When  ripe,  the  cane  is  cut,  the  leaves 
and  green  top  removed,  and  the  juice  expressed  by  passing 
the  cane  between  rollers,  arranged  somewhat  like  those  of  your 
clothes  wringer.  Lime  is  then  added  to  coagulate  the  impuri- 
ties, and  to  neutralize  any  acids  that  may  be  present.  The 
sweet  juice  is  then  boiled,  to  evaporate  some  of  the  water. 
The  scum  that  rises  is  removed.  When  enough  water  has 
evaporated,  so  that  the  solution  is  ready  to  crystallize,  it  is 
run  into  tanks,  where  it  cools,  and  crystals  of  cane  sugar 


CARBOHYDRATES 


227 


are  obtained.  The  liquid  that  does  not  crystallize  is 
molasses,  which  is  drained  off.  The  sugar  crystals  remain- 
ing are  "  raw  sugar."  Generally  the  raw  sugar  is  not  refined 
where  it  is  made,  but  is  shipped  to  a  large  sugar  refinery. 

Refining  sugar.  In  the  sugar  refineries  the  raw  sugar 
is  dissolved  in  hot  water,  and  filtered  to  remove  any  insoluble 
material.  It  then  forms  a  clear  sirup,  but  is  dark  in  color. 


FIG.  79.  —  View  in  a  sugar  cane  mill. 

To  remove  this  brown  coloring  matter,  the  sirup  is  passed 
through  large  cylinders  filled  with  bone  black. 

When  the  sirup  leaves  the  bone  black  filters,  it  is  not 
only  clear,  but  colorless.  It  must  now  be  evaporated  to 
crystallize  the  sugar.  Sugar  sirup  upon  boiling  undergoes 
a  chemical  change  called  hydrolysis,  in  which  one  molecule 
of  sucrose  combines  with  one  molecule  of  water  and  gives 
one  molecule  of  glucose  and  one  of  fructose.  Technically 


WEED    CHEMISTRY 15 


228 


CHEMISTRY   IN   THE    HOME 


this  change  is  called  inversion,  and  the  product  invert  sugar. 

Both  of  'these  substances  are  sugars,  but    they  are   not 

as  sweet  as  sucrose, 
nor  do  they  crystal- 
lize as  well.  It  is 
therefore  necessary  for 
the  sugar  refiner  to 
avoid  their  formation. 
To  do  this,  he  must 
avoid  heating  the 
sugar  to  a  high  tem- 
perature. He  must, 
however,  boil  the  sirup 
in  order  to  evaporate 
the  water  and  crystal- 
lize the  sugar. 

It  would  seem  as  if 
this  were  a  case  where 
the  manufacturer  was 
bound  to  find  trouble, 
whichever  way  he 
turned,  but  the  solu- 
tion of  the  problem 
is  easy.  The  sirup  is 
run  into  a  large  pan, 
so  arranged  that  it 
can  be  closed  air  tight 
and  then  the  air  is 
pumped  out.  We 
know  that  water  boils 
at  212°  F.  at  the 

FIG.  80-  —  Diagram  of  a  sugar  refining  plant.  ,.  , 

(After  Sadtier.)  ordinary  atmospheric 


CARBOHYDRATES 


229 


pressure.  If  the  air  pressure  is  lowered,  the  boiling  point 
is  also  lowered.  By  removing  the  air  from  over  the  sirup, 
the  boiling  point  of  the  sirup  is  lowered,  and  the  water  can 
be  evaporated  without  hydrolizing  or  inverting  the  sugar. 
It  is  necessary  to  pump  off  the  steam  as  fast  as  it  forms,  so 
as  to  keep  the  pressure  low.  You  must  remember  when 
cooking  fruits  that  sugar 
is  inverted  by  boiling,  and 
thus  much  of  the  sweet- 
ness is  lost. 

When  most  of  the  water 
has  evaporated,  the  sugar 
crystallizes,  and  these 
sugar  crystals  must  be 
separated  from  the  sirup. 
This  is  done  in  large  cen- 
trifugals (Fig.  81).  You 
know  that  when  mud  ac- 
cumulates on  the  rotating 
wheel  of  a  wagon,  there  is 
a  constant  tendency  for 
it  to  be  thrown  off,  and 
that  the  faster  the  wheel 

is  rotating,  the  greater  is  this  tendency.  This  is  due  to 
centrifugal  force,  and  this  principle  is  made  use  of  in  cen- 
trifugal separators,  used  not  only  in  the  sugar  industry,  but 
in  laundries,  creameries,  and  in  many  other  places. 

Imagine  two  large,  tall  saucepans,  the  one  fitting  inside 
the  other,  and  the  inner  one  made  of  wire  gauze  and  so 
arranged  that  it  can  be  rotated  while  the  outer  one  remains 
stationary.  The  sugar  sirup  containing  the  crystals  is 
put  into  the  inner  saucepan,  and  this  is  then  rapidly  rotated. 


230  CHEMISTRY   IN   THE   HOME 

There  is  a  great  tendency  for  everything  in  the  inner  vessel 
to  fly  out  through  the  gauze.  The  sirup  can  escape  through 
the  holes  in  the  gauze,  but  the  crystals  are  too  large  to  pass 
through,  and  so  remain  in  the  inner  cylinder. 

The  sugar  crystals  are  then  washed  by  throwing  a  little 
water  on  them,  so  as  to  free  them  from  the  sticky  sirup. 
The  sugar  is  now  pure  though  it  still  has  a  slight  yellow  tinge. 
To  counteract  this,  the  last  wash  water  is  often  colored  with 
a  little  ultramarine.  This  counteracts  the  slight  yellow 
tinge,  and  leaves  the  sugar  a  bluish  white.  You  must 
have  seen  clothes  treated  at  home  in  the  same  way,  and 
for  the  same  reason. 

The  sugar  crystals  are  now  run  into  the  upper  end  of 
a  large,  slightly  inclined  cylinder,  which  is  heated.  As 
this  cylinder  is  rotated,  the  crystals  tumble  over  each  other 
until,  when  they  have  reached  the  lower  end,  they  are  dry. 
The  granulated  sugar  is  now  ready  for  barreling. 

If  the  moist  crystals  are  pressed  together,  they  form  a 
solid  mass  that,  when  broken  up,  forms  lump  sugar.  If 
the  crystals  are  ground  to  a  fine  powder,  we  have  powdered 
sugar.  If  the  grinding  is  continued  until  a  very  fine  powder 
results,  we  call  it  confectioners'  sugar.  Rock  candy  consists 
of  large  crystals  of  cane  sugar.  It  is  obtained  by  allowing 
sirup  to  crystallize  slowly. 

Beet  sugar.  Sugar  cane  is  not  our  only  source  of  sugar. 
Much  of  the  sugar  that  you  use  comes  from  the  sugar  beet 
(Fig.  82).  In  many  countries  the  sugar  beet  has  been  culti- 
vated and  selected  until  the  best  specimens  may  contain 
as  much  as  16%  of  sugar.  The  beets  are  washed,  sliced, 
and  put  into  large  iron  vats,  called  diffusors.  Here  water, 
heated  to  140°  F.,  is  added,  and  the  sugar  diffuses  from  the 
beets  into  the  water.  The  sirup  thus  obtained  is  then 


CARBOHYDRATES 


231 


purified  and  crystallized  in  a  way  similar  to  that  used  with 
cane  sugar.  More  than  one  half  of  the  sugar  produced  in 
the  world  is  beet  sugar. 

Maple  sugar.  Many  farms  in  the  Northern  states  and 
Canada  contain  a  grove  of  sugar  maples,  Acer  saccharinum. 
In  the  spring,  when  the  sap  starts  to  flow,  the  farmer  "  taps  " 


FIG.  82.  —  Sugar  beets,     (a)  Wild.     (&)  Cultivated. 

these  trees.  That  is,  he  bores  a  hole  through  the  bark  into 
the  wood,  and  drives  a  spout  into  the  tree,  so  arranged  that 
the  sap  as  it  oozes  out  is  caught  in  a  pail  below.  This  sap 
contains  about  2%  of  cane  sugar.  The  sap  is  then  concen- 
trated by  heating  in  large  shallow  pans  until  it  contains 
60%  of  sugar,  when  it  is  poured  off  to  be  used  as  maple 
sirup.  Or,  it  is  concentrated  until,  on  cooling,  it  solidifies, 
which  gives  maple  sugar. 


232 


CHEMISTRY   IN   THE    HOME 


Maple  sugar  is  essentially  cane  sugar,  containing  a  little 
invert  sugar,  and  certain  substances  that  give  it  its  char- 
acteristic taste  and  color.  It  is  easily  adulterated  by  using 
cane  sugar  and  a  flavoring  extract  obtained  from  hickory 
bark.  About  6000  tons  are  produced  annually  in  the 
United  States. 


FIG.  83.  —  Collecting  sap  for  making  maple  sirup  and  sugar. 

Sorghum  sugar.  Small  quantities  of  sucrose  are  also 
made  from  the  sorghum  cane.  In  spite,  however,  of  exten- 
sive experiments  by  the  government  to  improve  both  the 
cane  and  methods  of  extraction,  the  production  of  sugar 
from  this  source  has  never  been  successful  commercially. 

Boiling  sugar.  Most  of  us  have  a  sweet  tooth,  and  a 
paragraph  that  will  help  us  to  enjoy  some  toothsome  dainties 
may  be  welcome. 


CARBOHYDRATES  233 

When  sugar  is  dissolved  in  a  small  amount  of  water,  and 
the  solution  boiled,  the  sugar  tends  to  grain  or  crystallize, 
as  the  water  evaporates.  When  we  wish  to  prevent  this, 
we  must  be  careful  not  to  stir  or  jar  the  solution.  The 
sirup  in  contact  with  the  sides  of  the  pan  becomes  slightly 
more  concentrated  than  the  rest,  and  therefore  crystalliza- 
tion starts  there.  If  these  crystals  are  allowed  to  remain, 
they  will  speedily  cause  the  entire  mass  to  become  crystal- 
line; they  must  therefore  be  removed  by  wiping  them  off 
with  a  damp  cloth.  The  addition  of  half  a  mustard 
spoonful  of  cream  of  tartar,  or  of  a  few  drops  of  lemon  juice* 
to  a  pound  of  sugar  will  help  to  prevent  this  crystalliza- 
tion. 

The  temperature  of  the  boiling  sugar  solution  slowly 
rises  as  the  water  evaporates.  When  the  temperature 
reaches  215°-217°  F.,  a  little  of  the  sirup,  when  pressed 
between  the  thumb  and  finger,  can  be  drawn  out  into  a  thin 
thread.  At  this  stage  the  sugar  is  suitable  for  boiled  icings. 
At  236°-238°  F.,  a  little,  dropped  into  cold  water,  forms  a 
soft  ball  that  can  be  rolled  between  the  fingers.  This  stage 
is  used  for  fondant.  At  310°  F.,  dropped  into  water,  it 
forms  a  mass  that  breaks  easily,  and  is  crisp.  At  this  point, 
called  the  crack,  it  crystallizes  very  easily,  so  that  it  is  well 
to  add  four  drops  of  lemon  juice  for  each  pound  of  sugar. 
This  stage  is  used  for  glace  nuts.  At  345°-350°  F.,  it  turns 
yellow-brown,  and  acquires  the  flavor  of  caramel.  It  now 
contains  practically  no  water,  and  burns  very  easily. 

These  four  stages  —  the  thread,  the  soft  ball,  the  crack, 
and  caramel  —  are  the  four  most  used  in  cooking.  The  ex- 
perienced cook  can  easily  recognize  them  by  the  behavior  of 
the  sirup,  but  the  use  of  the  thermometer  will  enable  even 
the  beginner  to  recognize  them  with  certainty. 


234  CHEMISTRY   IN   THE    HOME 

Maltose.  When  the  ptyalin  of  the  saliva  acts  upon 
starch,  maltose  is  formed.  This  sugar  has  the  same  formula 
as  sucrose,  with  the  addition  of  water,  C^IfeOii  •  H2O. 
Maltose  is  made  from  starch  by  the  action  of  malt  extract. 
When  seeds  germinate,  the  ferment  diastase  that  they  con- 
tain changes  their  starch  into  maltose,  on  which  the  young 
plant  feeds.  When  maltose  is  inverted,  only  glucose  results. 

Lactose.  Lactose,  milk  sugar,  C^H^On  •  H2O,  is  the 
substance  that  gives  milk  its  sweet  taste.  Cows'  milk  con- 
tains about  five  per  cent  of  lactose.  In  making  cheese,  the 
whey  of  the  milk,  which  contains  the  milk  sugar,  is  separated. 
This  whey  is  treated  with  chalk  and  aluminium  hydroxide, 
is  then  filtered,  and  the  clear  filtrate  evaporated.  On  stand- 
ing, the  milk  sugar  separates. 

The  souring  of  milk  is  due  to  the  action  of  bacteria  which 
change  the  lactose  to  lactic  acid. 

Milk  sugar  is  not  as  sweet  as  cane  sugar,  and  is  much 
less  soluble  in  water.  It  is  used  extensively  in  prepared 
infants'  foods,  and  in  the  pills  and  powders  of  the  druggist. 

Corn  products.  Under  the  general  name  of  glucose,  a 
number  of  different  carbohydrates,  mixed  in  varying  pro- 
portions, are  on  the  market.  They  are  all  made  from  starch 
by  hydrolysis.  More  than  50,000,000  bushels  of  corn  are 
annually  used  in  the  manufacture  of  starch  and  the  glucose 
products  made  from  it.  The  process  is  interesting,  as  it 
well  illustrates  how  in  a  modern  industry  chemistry  has  en- 
abled us  to  utilize  all  of  the  products  obtained.  It  is  this 
utilization  of  what  was  formerly  thrown  away,  that  marks 
one  great  result  of  modern  chemistry.  The  following  dia- 
gram shows  the  products  made  from  the  corn  kernel. 

The  corn  is  first  soaked  in  water.  This  softens  the  grain, 
and  dissolves  some  soluble  materials.  This  water  is  not 


CARBOHYDRATES  235 

thrown  away,  but  is  evaporated,  and  the  residue  used  in 
making  a  cattle  food. 

The  softened  corn  is  then  ground  coarsely,  so  as  not  to 
crush  the  germ,  and  then  thrown  into  water.  The  germ, 
being  light,  because  of  the  oil  that  it  contains,  floats,  and 
is  taken  off.  The  germs  are  then  dried  and  pressed,  and 
corn  oil  is  obtained.  This  is  used  in  making  soaps  and  in 


p; 

-.'.'•;•'.'•.•  .'.'1                                     "   "  \J  1—  ^- 

rch 
Gluten) 

GLUTEN 

[ 

1        1 

Oil  cake                          Corn  oil                                                                 Raw  sta 
(Cattle  Feed)         (Rubber  Substitute)                                              (Starch  and 

STARCH                               STARCH                           | 

Corn  Sirup  (Mixing) 
Corn  Sirup  (Crystal) 
Corn  Sugar 
Corn  and  Cane  Sirup 
Dextrins 
White 
Canary 
Dark  Canary 

*                                   ^X     t 

British  Gum                                                  Gluten  Feed 
Dry  Starches                                              (Cattle  Feed 
Pearl 
Powdered 
Laundry  Lump 
Thin  Boiling  Confectionery 
Corn  (Edible) 
Brewer's  Refined  Grits 

oilcloth,  and,  when  purified,  in  cooking  or  as  a  salad  oil. 
The  cake  remaining  in  the  press  is  ground  and  used  as  a 
cattle  food. 

The  hulls  are  then  separated  from  the  endosperm,  that 
white  part  of  the  grain  containing  the  starch,  dried,  and 
ground.  A  cattle  food  is  made  from  these  hulls,  mixed 
with  the  gluten  which  is  produced  later,  and  the  residue  left 
on  evaporating  the  softening  water. 

The  endosperm  is  finely  ground,  mixed  with  water,  and 
made  to  flow  through  long,  shallow,  slightly  inclined  troughs. 


236  CHEMISTRY   IN   THE   HOME 

Here  the  starch  and  gluten  separate,  because  of  their  dif- 
ferent specific  gravities.  The  gluten  is  used  as  a  cattle  food. 

The  starch  is  dried,  and  sold  as  edible  corn  starch,  and 
as  the  various  grades  of  laundry  starch.  The  pearl,  crystal, 
and  lump  laundry  starches  are  all  made  from  the  same 
stock,  their  different  appearances  being  caused  by  different 
methods  of  drying. 

Manufacture  of  dextrin.  If  this  starch  is  roasted,  dextrin 
is  produced.  The  different  varieties  of  dextrin,  as  white, 
yellow,  and  British  gum,  are  due  to  heating  to  a  higher  or 
lower  temperature,  and  by  varying  the  time  of  treatment. 
The  dextrins  are  used  as  adhesives,  as  in  the  gum  on  the  back 
of  postage  stamps,  as  sizes  in  the  textile  industry,  and  for 
thickening  the  colors  used  in  calico  printing.  The  crust  of 
bread  is  sweet  because  of  the  dextrin  that  it  contains. 

Manufacture  of  glucose.  To  prepare  glucose,  starch  is 
mixed  with  water,  a  small  amount  of  hydrochloric  acid 
added,  and  the  liquid  heated  under  pressure.  The  starch 
hydrolizes,  and  is  converted  into  dextrin  and  glucose. 

(C6H1005)n  +  n  H20  ^  (C6H12O6)n 

If  a  table  sirup  is  to  be  made,  the  conversion  is  stopped 
when  a  product  containing  50%  glucose  and  50%  dextrin 
is  obtained. 

The  hydrochloric  acid  is  next  neutralized  by  the  addition 
of  sodium  carbonate,  the  liquid  filtered,  decolorized  by  pass- 
ing it  through  bone  black  filters,  and  concentrated  to  the 
desired  thickness. 

If  a  solid  glucose  sugar  is  to  be  made,  the  inversion  is 
continued  until  most  of  the  dextrin  is  converted  into  glucose. 
It  is  then  purified  as  for  sirup,  and  evaporated  until  it  solidifies 
on  cooling. 


CARBOHYDRATES 


237 


Glucose  is  used  extensively  in  confectionery,  in  jams 
and  jellies,  pastes  and  sizes,  tanning  of  leather,  and  in  mak- 
ing vinegar.  It  is  only  three  fifths  as  sweet  as  cane  sugar, 
but  has  the  advantage  over  cane  sugar  of  being  absorbed 
directly  into  the  body,  requiring  no  digestion.  It  is  a  desir- 
able food,  but  should  be  sold  under  its  own  name,  and  not 
under  the  many  fanciful  names  with  which  it  appears  in 
commerce. 

Glucose,  dextrose,  and 
grape  sugar  occur  in  nature 
in  many  fruits.  The  hard 
white  particles  found  in 
raisins  are  glucose.  Fruc- 
tose, also  called  levulose  and 
fruit  sugar,  has  the  same 


FIG.  84.  —  Manufacture  of  potato  starch,      (a)  Rasping  machine,  (b)  Rasp- 
ing cylinder. 

formula  as  glucose,  C6Hi2O6,  but  its  physical  properties  are 
somewhat  different.     It  is  found  in  honey. 

Starch.  Just  as  business  men  store  up  a  certain  amount 
of  money  against  a  time  of  need,  so  plants  store  up  a  reserve 
of  food.  This  accumulation  of  food  is  largely  in  the  form 
of  starch  (C6Hi0O5).  It  is  found  in  the  roots,  bulbs, 
tubers,  and  sometimes  in  the  stems  and  leaves. 


238 


CHEMISTRY   IN   THE   HOME 


It  is  easily  separated  from  the  potato  by  grating  the  tuber, 
placing  the  pulp  in  a  cloth  bag,  and  washing  in  water.  The 
fine  grains  of  the  starch  pass  through  the  cloth  and  make 


FIG.  85.  — •  Shaking  table  for  separating  starch  from  potato  pulp. 

the  water  milky,  while  the  fiber  is  held  back.     On  settling, 
a  layer  of  starch  is  obtained. 

Starch  grows  in  fine  grains,  the  size  depending  on  the 
plant  from  which  it  is  obtained  (Fig.  86).     The  potato  starch 


. —  Different  kinds  of  starch  grains.     1,  Potato.     2,  Wheat.     3,  Rice. 


granule  has  an  average  diameter  of  3^0  °f  an  inch,  the  gran- 
ules of  wheat  starch  have  an  average  diameter  of  yoVir  °f  an 
inch,  and  the  granules  of  rice  starch  are  still  smaller.  The 


CARBOHYDRATES 


239 


identification   of    starch   under   the  microscope  makes    it 
possible    to    detect    many    forms    of    food    adulteration. 


FIG.  87.  —  (a)  Pepper  starch 
(angular  bodies)  adulterated 
with  bean  starch  (rounded). 


(&)  Characteristic  sap  vessels 
in  chicory  by  which  its  pres- 
ence in  coffee  is  detected. 


Starch  is  not  soluble  in  water.  On  heating  the  grains 
with  water  to  158°  F.,  the  granules  swell,  and  form  a  kind 
of  semi-solution,  as  in  the  case 
of  laundry  starch  or  starch  paste. 

When  heated  with  an  acid, 
starch  hydrolizes,  as  we  have 
already  seen  in  the  manufacture 
of  glucose.  This  change  of  starch 
to  sugar  also  takes  place  in 
seeds  when  they  germinate.  The 
change  is  caused  by  a  ferment 
contained  in  the  seed,  called 
dwfeut.  Every  woman  is  familiar  <«> J*** 
with  the  uses  of  starch  in  making 
foods,  in  baking  powder,  where  it 
is  used  as  a  filler,  for  laundry  purposes,  and  as  a  size  for 
stiffening  fabrics  in  the  textile  industry. 


starch  (angular  bodies). 
Courtesy  of  the  Scientific  American. 


240  CHEMISTRY   IN   THE   HOME 

The  saliva  contains  a  ferment  called  ptyalm.  When 
starch  is  brought  into  contact  with  this,  it  is  hydrolized,  with 
the  formation  of  dextrin  and  maltose.  Hence  the  impor- 
tance of  thoroughly  masticating  all  starchy  foods. 

Commercial  forms  of  starch.  Starch  appears  on  the  mar- 
ket not  only  under  its  own  name,  but  as  sago,  tapioca, 
arrowroot,  etc.  These  are  all  starches  obtained  from  some 
particular  plant.  Sago  is  made  from  a  palm.  In  manufac- 
ture, it  has  been  heated  so  that  it  is  difficult  to  find  separate 
starch  grains  in  it. 

Tapioca  is  made  from  the  cassava  plant.  The  starch 
is  first  separated  from  the  woody  fiber  of  the  plant  by  grind- 
ing and  washing  in  water.  Before  the  starch  becomes  dry, 
it  is  heated,  with  the  result  that  the  starch  grains  are  broken 
up,  and  the  starch  is  left  in  the  familiar  form  in  which  we 
find  it  in  the  market. 

Arrowroot  is  usually  obtained  from  a  plant  called  Canna 
indica,  which  grows  mainly  in  tropical  regions.  It  is  also  ob- 
tained in  Bermuda  from  the  Maranta  arundinacea.  These 
arrowroots  are  used  largely  in  invalid  foods.  They  form 
a  firm,  semi-translucent  mass  when  heated  in  a  small  quantity 
of  water.  The  name  comes  from  the  fact  that  the  bruised 
stems  of  the  plant  were  used  as  a  poultice  for  wounds  caused 
by  arrows. 

Cellulose.  Cellulose  forms  the  chief  part  of  wood.  It  is 
the  building  material  of  all  plants,  and  comprises  the  cell 
wall.  Absorbent  cotton  and  the  best  grades  of  filter  paper 
are  nearly  pure  cellulose. 

Pure  cellulose  is  white,  insoluble  in  water,  and  permanent 
in  the  air.  Treated  with  a  mixture  of  strong  nitric  and  sul- 
phuric acids,  cellulose  is  converted  into  a  nitrate  of  cellulose. 
This  is  guncotton,  a  violent  explosive  used  in  torpedoes. 


CARBOHYDRATES  241 

One  of  these  cellulose  nitrates  is  soluble  in  a  mixture  of 
alcohol  and  ether,  and  forms  collodion.  This  is  used  in 
photography  and  surgery.  If  a  small  amount  of  castor  oil 
is  added  to  collodion,  it  remains  flexible  when  it  dries,  and  is 
then  used  to  cover  cuts  in  the  skin. 

Celluloid.  By  adding  camphor  to  guncotton,  an  elastic  mass 
called  celluloid  is  obtained.  When  hot,  this  is  plastic,  and  'can 
be  rolled  out  into  sheets,  or  formed  into  combs,  knife  handles, 
and  a  multitude  of  materials  used  in  the  home.  It  can  be 
colored,  and  made  either  transparent  or  opaque.  In  using 
celluloid,  do  not  forget  that  it  contains  guncotton,  and  will 
therefore  burn  with  great  violence.  Moreover,  since  it  is 
a  nitrate  and  contains  a  large  amount  of  oxygen,  the  flame 
once  started  requires  no  outside  supply  of  oxygen.  Burning 
celluloid  therefore  cannot  be  extinguished  by  smothering. 
Moving  picture  films  are  made  on  thin  sheets  of  celluloid, 
and  the  many  disastrous  fires  that  have  occurred  in  moving 
^picture  theaters  have  been  due  to  the  difficulty  with  which 
burning  celluloid  is  extinguished. 

Manufacture  of  handmade  paper.  The  use  of  some  form 
of  paper  dates  from  the  earliest  antiquity.  We  have  papyrus 
rolls,  written  on  by  the  Egyptians,  that  date  from  4000  B.C. 
This  kind  of  paper  was  made  from  the  papyrus  reed  that 
grows  on  the  banks  of  the  Nile.  The  Chinese  have  long 
used  a  paper  made  from  the  inner  bark  of  the  mulberry  tree. 

In  the  Middle  Ages,  paper  was  made  from  linen  by  mixing 
the  linen  fibers  with  enough  water  to  form  a  thin,  milklike 
liquid.  This  was  poured  on  a  wire  sieve  of  the  size  that  they 
wished  the  finished  sheet  to  be.  The  water  ran  through, 
but  the  fibers  remained  in  the  sieve.  This  sheet  was  then 
placed  on  a  piece  of  felt  and  pressed.  When  dry,  a  sheet 
of  paper  resulted. 


242  CHEMISTRY   IN   THE    HOME 

Paper  made  in  this  way  was  porous,  like  blotting  paper, 
and  could  not  be  used  to  write  on,  as  the  ink  would  spread. 
To  overcome  this,  the  dried  sheet  was  passed  through  a 
thin  solution  of  gelatin,  to  size  it.  This  process  is  slow  and 
expensive,  and  to-day  only  the  most  expensive  papers  are 
made  in  this  way. 

Manufacture  of  machine  paper.  Modern  paper  is  made 
on  the  Fourdrinier  machine.  The  crude  material  used  is 
rags,  wood,  esparto  grass,  old  paper,  cotton  refuse,  and  many 
other  fibrous  materials.  The  raw  stock  used  depends  on 
the  grade  of  paper  wished.  The  all-rag  papers  are  the 
best,  but  also  the  most  expensive.  Newspaper  is  made 
from  wood,  and  is  the  cheapest  paper  made. 

In  making  a  rag  paper,  the  rags  are  first  sorted  by  hand, 
the  buttons  cut  off,  and  the  cloth  cut  into  small  pieces. 
It  then  goes  to  the  duster,  where  it  is  beaten  to  remove  as 
much  dirt  as  possible.  Here  it  may  lose  as  much  as  five  per 
cent  of  its  weight.  The  rags  then  pass  to  the  rag  boiler,  where 
they  are  treated  with  sodium  hydroxide  or  with  lime.  Much 
of  the  coloring  matter  is  here  removed  while  the  rags  are 
washed.  They  then  go  to  the  beating  engine,  where  knives 
cut  them  up  and  the  stirring  separates  them  into  individual 
fibers.  Here  also  the  pulp  is  bleached,  or  colored,  as  may  be 
required. 

This  pulp,  mixed  with  much  water,  is  flowed  upon  an 
endless  woven  screen  of  wire,  which  travels  rapidly  under 
the  box  containing  the  pulp.  The  water  drains  through, 
while  the  fibers  felt  together  to  make  an  endless  sheet  of 
paper.  Seventy  feet  of  fine  paper,  or  600  feet  of  newspaper, 
are  made  a  minute. 

As  the  paper  passes  on,  it  passes  between  rollers  that 
squeeze  out  the  water.  At  the  turning  point  of  the  endless 


WEED    CHEMISTRY 16  243 


244  CHEMISTRY   IN   THE    HOME 

wire  belt,  the  paper  leaves  it,  and  passes  over  a  number  of 
hollow  iron  cylinders,  heated  by  steam.  Here  it  is  dried. 
It  then  passes  between  heavy  polished  steel  rollers  to  smooth 
it,  after  which  it  is  cut  into  sheets.  This  gives  a  porous 
paper. 

If  a  writing  paper,  or  a  paper  on  which  to  print  illustra- 
tions containing  fine  lines  is  needed,  the  paper  must  be  sized. 
Glue  or  rosin,  and  some  filler,  as  clay,  is  then  added  to  the 
paper  pulp.  When  such  a  sized  paper  passes  through 
the  last,  or  calendering  rolls,  the  paper  is  given  a  smooth 
or  even  a  glossy  surface.  So  much  clay  is  sometimes  added 
that,  if  such  "  supercalendered  "  paper  is  bent,  it  will  crack. 
You  have  probably  noticed  the  disagreeable  odor  that  some 
paper  gives  off  when  damp.  This  is  because  of  the  glue  used 
in  the  sizing. 

Wood  pulp  paper.  Rag  paper  is  too  expensive  to  be  used 
in  newspapers.  For  this  purpose  paper  made  from  wood 
pulp  is  used.  Wood  pulp  is  of  two  kinds,  mechanical  and 
chemical. 

Mechanical  pulp  is  simply  ground  wood.  This  is  made 
by  splitting  poplar  or  spruce  into  small  pieces  and  grinding 
them  against  a  wet  grindstone.  The  wood  forms  a  powder 
fine  as  flour.  The  fiber  is  so  short  that  it  would  not  make 
paper  by  itself,  but  it  is  useful  as  a  filler. 

Chemical  wood  pulp  is  made  by  chipping  wood,  and  then 
heating  these  chips  in  solutions  of  sodium  hydroxide  or 
lime  sulphite  in  large  vats  under  pressure.  These  chemicals 
dissolve  the  materials  that  hold  the  wood  fibers  together. 
After  the  "  cooking  "  is  complete,  which  takes  from  six  to 
eighteen  hours,  the  mass  is  thrown  into  water.  It  is  then 
screened,  to  remove  lumps,  and  used  in  the  same  way  that 
rag  pulp  is. 


a.    Paper  making  machine. 


b.    Drying  and  finishing  the  paper. 
Fig.    89.  —  Paper  making. 

245 


246  CfrtfMlSTRY   IN  THE   HOME 

Common  newspaper  contains,  about  25%  of  chemical 
and  75%  of  mechanical  wood  pulp.  Sulphite  wood  pulp 
is  largely  used  in  book  papers.  Blotting  paper  contains 
no  size.  Filter  paper  is  made  from  the  best  grade  of  linen 
fiber,  and  contains  no  size.  The  finish  put  on  some  writing 
papers,  as  linen  finish,  is  made  by  passing  the  paper  between 
rolls  that  have  the  desired  design  engraved  on  them. 

Saccharin.  Saccharin,  C7H5O3SN,  is  not  a  sugar,  but  is  a 
compound  that  has  an  exceedingly  sweet  taste.  It  is  about 
500  times  as  sweet  as  cane  sugar.  It  is  sometimes  mixed 
with  glucose  in  cheap  candy  to  make  the  product  as  sweet 
as  if  cane  sugar  had  been  used.  Such  a  use  is  of  course 
fraudulent.  It  is  also  used  by  diabetic  persons  who  must 
avoid  the  use  of  sugar.  It  has  no  nutritive  value  and 
is  considered  a  poisonous  and  deleterious  ingredient  in 
foods. 

Carbohydrates  as  foods.  The  carbohydrates  are  very 
largely  used  as  foods.  In  nature,  they  occur  in  both  soluble 
and  insoluble  forms.  The  soluble  forms,  as  the  sugars  of 
fruits  and  honey,  require  little  action  of  the  digestive 
juices ;  indeed,  many  of  these  soluble  forms  require  none,  but 
are  absorbed  unchanged  by  the  body  to  be  used  in  giving 
heat  and  energy.  The  insoluble  forms  are  mainly  starch 
and  cellulose.  Before  these  can  be  made  available  in  our 
bodies,  they  must  be  m^de  soluble.  Our  digestive  juices 
are  not  able  to  do  this  to  cellulose,  and  so  this  is  unavailable 
as  a  food  for  us.  In  our  digestive  tract  starch  can,  however, 
be  made  soluble,  and  it  forms  one  of  our  most  used  foods. 
Cooking  starchy  foods  starts  this  action  by  breaking  up 
the  starch  grains,  and,  if  prolonged,  converts  some  of  the 
starch  into  other  soluble  carbohydrates,  as  dextrin  and 
glucose,  thus  aiding  the  action  of  the  digestive  juices. 


CARBOHYDRATES  247 

Proteins.  One  large  group  of  compounds  found  in  all 
animal  and  most  vegetable  matter  is  the  proteins.  They 
contain  carbon,  oxygen,  hydrogen,  nitrogen,  sulphur,  and 
sometimes  phosphorus.  Nitrogen  is  the  essential  element 
which  distinguishes  the  proteins  as  a  class  of  food  compounds. 
Albumin,  casein,  gluten,  gelatin,  and  peptone  are  all  examples 
of  proteins. 

Ptomaines.  When  certain  bacteria  act  upon  proteins,  they 
cause  putrefaction,  forming  ptomaines.  These  ptomaines 
are  violently  poisonous  bodies,  and  the  eating  of  meat  con- 
taining them  causes  ptomaine  poisoning,  which  often  results 
fatally.  The  heat  of  summer  accelerates  the  growth  of 
bacteria,  and  hence  causes  the  quick  decay  of  food.  This 
is  the  reason  why  ptomaine  poisoning  is  so  much  more 
common  in  summer. 

Albumin.  Albumin  occurs  in  many  of  the  soft  parts  of 
the  bodies  of  animals.  The  white  of  egg  is  almost  pure 
albumin  and  water.  The  blood  also  contains  it.  It  is  solu- 
ble in  water,  and  is  coagulated  by  both  heat  and  alcohol. 

Casein.  Casein  is  found  in  milk.  It  resembles  albumin, 
but  is  not  coagulated  by  heat.  It  is  prepared  by  passing 
sweet  milk  through  a  centrifugal  cream  separator,  to  free 
it  from  butter  fat.  An  acid  is  then  added,  which  precipitates 
the  casein  in  the  form  of  a  curd.  It  is  then  washed,  to  free 
it  from  milk  sugar  and  acid,  and  dried.  It  keeps  indefinitely, 
if  kept  dry. 

It  is  used  extensively  as  an  adhesive,  in  buttons,  in  paper 
making,  in  casein  paints,  and  in  preparing  plastic  masses. 
Paper  bottles,  used  to  contain  milk,  are  made  by  soaking 
paper  in  a  solution  of  casein,  and  then  exposing  it  to  the 
vapor  of  formaldehyde.  This  makes  the  casein  waterproof. 

Casein  paints  are  made  by  dissolving  casein  in  borax  or 


248  CHEMISTRY   IN   THE    HOME 

sodium  hydroxide,  and  adding  a  filler  and  a  pigment.  Clay, 
lime,  or  powdered  feldspar  are  used  as  fillers,  and  lamp 
black,  cobalt  blue,  or  chrome  green  as  pigments.  It  is 
necessary  to  pick  out  a  filler  and  a  pigment  that  will  not 
be  affected  by  the  alkali  used.  These  paints  dry  hard,  may 
be  rendered  waterproof  with  formaldehyde,  and  are  cheap. 

Gelatin.  Gelatin  is  an  animal  jelly.  It  is  the  chief  con- 
stituent of  glue.  It  is  made  by  heating  the  bones  and 
skins  of  animals  in  water  for  a  long  time.  These  animal 
products  contain  collagen  and  ossein,  which,  on  long  boiling, 
change  to  gelatin.  The  solution  obtained  is  cooled,  when  it 
gelatinizes.  The  water  is  driven  off,  and  dry  gelatin  remains. 

Gluten.  If  you  will  place  a  handful  of  flour  in  a  cloth 
bag,  and  knead  it  under  water,  the  starch  grains  will  pass 
through  the  cloth  and  make  the  water  milky.  There  will 
remain  in  the  cloth  a  tough,  yellowish  substance  called 
gluten.  Some  flours,  as  those  used  to  make  macaroni,  con- 
tain a  large  percentage  of  gluten.  It  is  gluten  that  makes 
it  possible  to  make  bread  light.  When  flour  is  mixed  with 
water,  it  is  the  gluten  that  forms  the  pasty  dough  that 
entangles  the  bubbles  of  carbon  dioxide  gas. 

Alkaloids.  Most  of  the  nitrogenous  compounds  found  in 
nature  are  foods.  One  exception  is  the  class  of  bodies  known 
as  alkaloids.  These  are  feeble  bases,  and  combine  with 
acids  to  form  salts,  which  as  a  rule  crystallize  easily.  They 
are  slightly  soluble  in  water,  and  readily  soluble  in  alcohol. 

The  alkaloid,  theine  or  caffeine,  present  in  tea  and  coffee, 
is  the  stimulating  substance  found  in  these  beverages. 
Theobromine,  a  similar  alkaloid,  is  found  in  the  cocoa  bean. 
Nicotine,  found  in  tobacco,  is  intensely  poisonous.  Co- 
caine is  prepared  from  the  leaves  of  the  coca  plant.  It  is 
used  by  physicians  in  the  form  of  cocaine  hydrochlorate 


CARBOHYDRATES  249 

as  a  local  anaesthetic ;  that  is,  if  applied  to  some  part  of  the 
body,  as  the  gums,  it  makes  that  part  of  the  body  insensible 
to  pain.  Quinine  and  cinchonine  are  obtained  from  the 
bark  of  the  cinchona  tree,  and  are  used  as  specifics  in 
malaria.  All  the  above  more  or  less  poisonous  bodies  are 
alkaloids. 

SUMMARY 

Carbohydrates  are  compounds  containing  six  atoms  of  carbon,  or  a 

multiple  of  six,  and  hydrogen  and  oxygen  in  the  proportion  in 

which  they  occur  in  water.     Sugar,  starch,  and  cellulose  are 

important  carbohydrates. 
Sucrose  comes  from  the  sugar  beet,  the  sugar  cane,  and  from  the 

sugar  maple. 
Glucose,  or  grape  sugar,  is  made  from  starch  by  heating  it  with  a 

minute  quantity  of  acid. 
Fructose,  or  fruit  sugar,  is  found  in  honey. 
Maltose  is  malt  sugar. 
Lactose  is  milk  sugar. 
Hydrolysis  is  the  splitting  up  of  a  molecule  caused  by  its  combining 

with  a  molecule  of  water. 
Inversion  is  the  hydrolysis  of   a  sugar  solution.     Invert  sugar  is 

produced. 

Dextrin  is  made  by  heating  dry  starch.     It  is  used  as  an  adhesive. 
Paper  is  made  from  cellulose. 
Saccharin  is  not  a  sugar.     It  is  500  times  as  sweet  as  cane  sugar. 

It  has  no  nutritive  value  and  is  harmful. 
Cellulose  forms  part  of  the  woody  part  of  plants.     Absorbent  cotton 

is  nearly  pure  cellulose. 
Proteins  are  nitrogenous  organic  bodies.     Albumin  and  casein  are 

examples. 

Exercises 

1.  Why  does  the  crust  of  bread  taste  sweet? 

2.  Is  there  any  difference  between  caramel  and  burnt  sugar? 

3.  In  cooking  cranberries,  when  should  the  sugar  be  added  and 
why? 


CHAPTER  XXIII 
FOODS 

Food  defined.  One  great  difference  between  animals 
and  plants  is  in  the  food  that  each  can  use.  Plants  are 
able  to  build  up  from  carbon  dioxide,  water,  and  mineral 
salts,  the  most  complex  compounds.  Animals  cannot  do 
this,  but  are  dependent  for  food  on  products  that  plants 
have  elaborated  for  them.  Plants  can  get  along  without 
animals,  but  animals  cannot  get  along  without  plants. 

The  requirements  of  our  bodies  are  similar  to  those  of 
other  animals.  We  need  food  to  repair  the  cells,  to  build 
up  new  tissue,  and  to  furnish  energy  and  heat  to  the  body. 
Food  may,  therefore,  be  defined  as  anything  which  will 
build  up  body  tissue,  and  furnish  it  with  heat  and  energy. 
This  food  must  be  both  organic  and  inorganic. 

Inorganic  foods.  As  about  65%  of  the  weight  of  the 
body  is  water,  we  require  large  amounts  of  this  to  replace 
the  loss  that  is  continually  taking  place.  We  take  large 
amounts  of  water,  both  directly  as  a  beverage,  and  in  the 
food  that  we  consume. 

The  skeleton  of  the  body  is  largely  calcium  phosphate, 
and  the  teeth,  blood,  and  tissues  all  contain  compounds 
of  iron,  sodium,  and  chlorine.  The  total  of  the  mineral 
constituents  is  about  6%  of  the  weight  of  the  body.  This 
mineral  matter  is  supplied  to  us  in  our  food.  Almost  any 
diet  will  give  more  than  we  require,  for  vegetables  all  con- 
tain mineral  matter  that  they  have  taken  from  the  soil. 

250 


FOODS 


251 


MINERAL  CONSTITUENTS   OF  MEATS,   FRUITS,   AND 

VEGETABLES  IN   PERCENTAGE   OF  THE   EDIBLE 

PORTION J 


FOOD 

CaO 

MgO 

K20 

Na2O 

P2O5 

Cl 

S 

Fe 

Apples   . 

.014 

.014 

.15 

.02 

.03 

.004 

.005 

.0003 

Beets      .     .     . 

.03 

.033 

.45 

.10 

.09 

.04 

.015 

.0006 

Cabbage     .     . 

.068 

.026 

.45 

.05 

.09 

.03 

.07 

.0011 

Carrots 

.077 

.034 

.35 

.13 

.10 

.036 

.022 

.0008 

Cauliflower     . 

.17 

.02 

.27 

.10 

.14 

.05 

.085 



Grapes  .     .     . 

.024 

.014 

.25 

.03 

.12 

.01 

.024 

.0013 

Lentils        .     . 

.15 

.17 

1.05 

.08 

1.00 

.05 

.28 

.0086 

Meats    .     .     . 

.011 

.03 

.3 

.057 

.33 

.03 

.13 

.002 

Muskmelons   . 

.024 

.020 

.283 

.082 

.035 

.041 

.014 

0003 

Parsnips 

.09 

.07 

.70 

.01 

.19 

.03 

.057 



Spinach      .     . 

.09 

.08 

.94 

.20 

.13 

.02 

.041 

.0032 

Squash  .     .     . 

.02 

.01 

.17 

.002 

.005 

.02 

.014 

.0008 

Strawberries    . 

.05 

.03 

.18 

.07 

.064 

.01 

.0009 

Classes  of  organic  foods.  Our  organic  foods  may  be 
divided  into  three  main  classes :  carbohydrates,  fats,  and 
protein.  We  get  the  carbohydrates  in  the  form  of  starch 
and  sugar  from  potatoes,  corn,  beans,  bread,  and  many 
other  sources.  In  the  body,  the  carbohydrates  are  burned 
to  furnish  heat  and  power.  If  an  excess  is  used,  the  body  has 
the  power  to  turn  it  into  fat,  and  this  is  stored  in  the  body. 

We  obtain  fats  in  the  form  of  butter,  oils,  fat  of  meat, 
and  nuts.  Most  vegetables  contain  little  or  no  fat.  In  the 
body,  fats,  like  carbohydrates,  are  burned  to  furnish  heat 
and  energy.  They  are  a  more  concentrated  food,  for  one 
pound  of  fat  is  roughly  equivalent  to  two  and  a  quarter 
pounds  of  carbohydrates  in  available  energy.  The  normal 
human  body  contains  about  15%  of  fat.  If  more  fat  is  eaten 
than  can  be  oxidized,  the  excess  may  be  stored  in  the  body. 
1  From  a  table  compiled  by  Henry  C.  Sherman. 


252 


CHEMISTRY   IN   THE    HOME 


OtTiu  of  f<p«rime«  SMIMM 
A.C.Tnx:f>trtv 

COMPOSITION  OF  FOOD  MATERIALS. 

P.ot...  Fit          C«rt>ot.,<!rlt«         Art 

SUGAR 


COMPOSITION  OF  FOOD  MATERIALS. 


FIG.  90.  —  Composition  of  sugar 
products. 


FIG.  91.  —  Composition  of  bread. 


COMPOSITION  OF  FOOD* MATERIALS. 


U.  S.  DwrtfMM  ot  Agfkutturt  P-e 

Otf«  ol  E,p«.m!nt  SU.IOM  C.FU 

A  c.  T.ot  O..iclof  bt*tbO«|lM( 

COMPOSITION  OF  FOOD  MATERIALS. 


CORN  WHEAT 

r:!0.8  Water:10< 


P'otfin:IOO  Protein-1?; 


BUCKWHEAT 

Protein.lOO-.-c-WiierJZ.e       |6Z5( 


OAT 

11.0          l59bc,L0.,ts       Water  120 - 
Ftt:5.0-Jfr—Protein:\\.6        «•">«»    Prouin.  g 


RVC         h,dr,te$..77.o\ 

Water:  10.5  *«—  Ash 

'«ta«i 


1620  ( 


FIG.  92.  —  Composition  of  vegetables.     FIG.  93.  —  Composition  of  cereals. 


FOODS 


253 


t  »i  i  ipi'imtM  Stit.or,s  C. '   UNGW08TNT 

A.  C.  Tru«:  Dii««»r  Enptrl  in  CM.».  o(  Notirt.on  ln,m^l,». 

COMPOSITION  OF  FOOD  MATERIALS 


CREAM  CHEESE  COTTAGE  CHEESE 

ater:  34  2-v__..— ^a 

,t.in:2S.9w^-».0 


d rates:  2. 


!.  Dtprlmtrt  Of  Atmultliie 

(iceoir.»Nime*Sut«»il 

AC.Tru.  Ot'tctti 

COMPOSITION  OF  FOOD  MATERIALS. 

sum    ma 


FIG.  94.  —  Composition  of  eggs  and         FIG.  95.  —  Composition  of  fish, 
cheese. 


U.S.  Ocpntntnt  ot  Agriculture  Prei 

COMPOSITION  OF  FOOD*  MATERIALS. 
tSBS     nnrnn     r'vi     ^^3 


VEGETABLE  OILS. AS  BACON 

OLIVE  ,  Protein. 9.4- 

PEANUT,  Water.l68 

COTTONSEED 


4060  MLOIIU  nil  roun 


A.  C.  True-  D.nctor 

COMPOSITION  OF  FOOD  MATERIALS. 


FIG.  96.  —  Composition  of  fats.          FIG.  97.  —  Composition  of  meats. 


254  CHEMISTRY   IN   THE    HOME 

We  get  protein  from  the  white  of  egg,  from  lean  meat, 
and  such  vegetable  foods  as  peas,  beans,  and  the  gluten 
of  flour.  The  function  of  protein  in  the  body  is  to  build 
and  repair  the  tissues,  and  it  is  the  only  food  that  can  do  this. 
It  can  also  be  burned  in  the  body  to  furnish  heat.  This 
is  not  economical,  as  both  fats  and  carbohydrates  are  cheaper 
sources  of  heat. 

Analogy  of  the  motor.  In  some  ways  our  bodies  resemble 
the  gasoline  motor  that  drives  a  car.  If  we  wish  our  motor 
car  to  run  properly,  we  must  see  that  it  has  the  proper  fuel 
and  use  this  in  the  right  amount.  If  we  use  too  much  fuel, 
our  car  does  not  run  well,  and  much  of  the  fuel  escapes  un- 
burned.  The  same  thing  is  true  of  our  bodies.  If  we  over- 
load our  stomachs,  we  are  dull  and  logy,  and  cannot  do  our 
work  properly. 

If  we  wish  our  car  to  run  properly,  we  must  carefully 
adjust  the  proportions  of  air  and  gasoline,  and  see  that  all 
the  bearings  are  properly  oiled.  So  with  our  bodies,  if 
we  wish  them  to  run  well,  we  must  use  all  of  the  different 
foods  in  the  proper  proportions,  and  not  limit  our  diet  to 
any  one  class. 

If  we  are  using  our  car  to  carry  heavy  loads  up  steep  hills, 
we  must  feed  more  gasoline  to  the  motor.  So  too,  if  we  are 
doing  heavy  manual  work,  our  bodies  require  more  fuel- 
food  and  also  a  slight  increase  in  building-food,  than  if  we 
are  doing  office  work  all  day  long. 

One  great  difference  between  a  car  and  our  bodies  is 
found  in  the  result  which  follows  neglect.  If  we  abuse  a 
car  by  neglecting  to  oil  it  properly,  the  car  stops,  and  we 
have  a  heavy  repair  bill  to  pay.  We  may  abuse  our  bodies, 
and  for  a  while  the  body  will  struggle  along,  but  in  the  end 
the  result  is  the  same.  We  have  a  heavy  doctor's  bill  to 


FOODS  255 

pay,  but  unfortunately  the  physician  cannot  put  a  new  part 
in  our  bodies,  as  the  mechanic  can  in  a  car.  He  can  only 
patch  them  up,  and  consequently  we  may  be  inefficient  as 
long  as  we  live. 

A  tire  that  will  give  5000  miles  of  service  under  ordinary 
conditions  will  give  but  200  miles  when  used  in  a  race. 
Our  bodies,  too,  are  meant  to  be  used  moderately.  If  we 
burn  the  candle  at  both  ends,  it  can  be  expected  to  last  only 
half  as  long. 

Of  course  our  body  is  much  more  than  a  machine,  for 
we  have  the  power  to  think,  and  intellectual  and  spiritual 
powers  that  no  machine  has.  But,  even  in  this  field,  if 
we  wish  to  develop  our  powers  to  the  utmost,  we  must  remem- 
ber that  the  first  requirement  is  a  sound  body,  and  that 
a  sound  body  is  best  obtained  by  the  use  of  proper  foods  in 
correct  amounts. 

Efficiency  and  economy.  Large  manufacturers  do  not 
buy  coal  solely  by  the  ton.  They  have  the  coal  analyzed, 
and  its  power  to  give  energy  determined.  They  do  not 
rely  altogether  on  price.  Some  coal  at  $4.00  a  ton  is  cheaper 
than  other  coal  at  $3.00  a  ton,  for  it  contains  more  heat 
units;  that  is,  when  burned  it  will  give  much  more  heat 
than  the  coal  sold  at  the  lower  price  per  ton.  Its  appearance 
will  not  tell  us  this;  it  must  be  analyzed. 

The  same  thing  is  true  of  foods.  It  does  not  follow  that 
the  appearance  and  taste  of  food  is  an  indication  of  its  nutri- 
tive value.  To  determine  its  value  to  us,  we  must  analyze 
it  and  find  the  quantities  and  proportions  of  the  different 
food  constituents  it  contains,  and  the  amount  of  available 
energy  it  will  yield  to  the  body.  We  must  also  know  the 
requirements  of  the  body,  and  we  are  then  in  a  position  to 
provide  wholesome  food  in  the  proper  amounts.  By  know- 


256 


CHEMISTRY   IN   THE    HOME 


ECONOMY   IN   BUYING   FOODS: 
I.     BUILDING   STUFFS 


FOOD 

COMPARATIVE  COST 

Oranges 

Salt  Pork,  Fat 
Celery 

ing  the  food  value  of  different  foods  in  the  market,  we  shall 
be  able  to  buy  nourishment  economically. 

The  two  charts  (Figs.  98A  and  98B)  are  intended  to  give 
an  idea  of  the  economic  values  of  food  from  two  stand- 
points. No.  1 
considers  the 
question  from 
the  standpoint 
of  Building  Ma- 
terial; No.  2 
takes  into  ac- 
count the  cost  of 

the  Energy  Material,  or  stuffs  found 
in  the  different  foods.  Since  most 
foods  provide  for  us  both  building 
materials  and  energy,  these  charts 
should  be  studied  together.  It 
wo^uld  be  incorrect  to  attempt  to 
get  results  from  either  chart  to  the 
exclusion  of  the  other. 

The  amount  of  building  stuff  in 
each  food  in  chart  No.  1,  or  energy 
stuff  in  each  food  in  chart  No. 
2,  is  the  same.  The  only  varia- 
tions shown  in  these  charts  are 
in  the  prices  which  we  pay  for 

these  materials,  as  represented  by  the  black  bars  of  different 
lengths. 

A  little  perusal  will  bring  out  the  fact  that  the  foods  found 
nearest  the  top  of  each  chart  are  the  most  expensive  and  the 
more  economical  ones  are  found  toward  the  bottom  of  the 
list. 


Apples 

Corn,  Canned 

Oysters 

Eggs 

Cabbage 

Beef,  Sirloin 

Pork,  Smoked  Ham 

Mutton 

Turnips 

Rice 

Milk 

Potatoes 

Beef,  Dried 

Cod,  Fresh 

Pork,  Loin 

Beef,  Round 

Beef,  Flank 

Wheat  Bread 

Wheat  Breakfast  Food 

Cheese 

Salmon 

Cod,  Salt 

Beef,  Stew  Meat 

Corn  Meal 

Oatmeal 

Beans 

FIG.  98A.  — The  cost  of  the 
same  amount  of  building 
stuffs  in  different  forms  of 
foods. 


FOODS 


257 


Although  the  number  and  range  of  foods  in  these  small 
tables  is  necessarily  limited,  the  lesson  need  be  no  less  impres- 
sive. It  must  be  remembered  that  only  the  financial  side 
of  the  question  is  here  considered  and  that  digestion  and 

ECONOMY   IN   BUYING  FOODS: 
II.    ENERGY   STUFFS 


FOOD 


COMPARATIVE  COST 


Oysters  ••••••••••••••••••«•••••••••••••••••••••  55  i 

Celery 

Cod,  Dressed 

Oranges 

Eggs 

Halibut 

Beef,  Dried 

Bananas 

Beef,  Sirloin 

Corn,  Canned 

Mutton 

Cabbage 

Cod,  Salt 

Beef,  Round 

Beef,  Flank 

Pork,  Smoked  Ham 

Salmon,  Canned 

Pork,  Loin 

Milk 

Apples 

Cheese 

Turnips 

Beef,  Stew  Meat 

Butter 

Rice 

Potatoes 

Wheat  Bread 

Wheat  Breakfast  Food 

Pork,  Salt 

Corn  Meal 

Beans  •      . 

Oatmeal  L  \<t 

FIG.  98B.-The  cost  of  the  same  Calories.     The  energy  that  the 

amount  of  energy  stuffs  in  differ-    food  will  give  when  Oxidized   in 
ent  forms  of  foods.  ,      .       ,  , 

the  body  is  thus  determined. 

Respiration  calorimeter.  To  study  the  requirements  of  the 
body  under  different  conditions,  the  respiration  calorimeter 
is  used.  One  of  the  most  famous  of  these  is  the  one  at  Wes- 
leyan  University,  built  by  Professors  Atwater  and  Rosa.  It 
is  a  copper-lined  box,  7  feet  long,  4  feet  wide,  and  6  feet  4 
inches  high.  It  is  so  arranged  that  a  man  can  live  in  it 


personal  idiosyncrasies  are  indi- 
vidual problems ;  it  is  believed, 
however,  that  a  family  that  cares 
to  live  economically,  can  get 
enough  in  variety  and  substance 
in  the  lower  two  thirds  of  these 
charts,  to  nourish  them  palata- 
bly, economically,  and  well. 

Calories  in  food.  The  energy 
value  of  food  has  been  deter- 
mined by  burning  the  food  and 
determining  the  amount  of  heat 
given  off.  This  is  measured  in 


258  CHEMISTRY   IN   THE   HOME 

for  days,  either  resting,  or  doing  work.  All  of  the  necessary 
food  can  be  passed  in  to  him,  the  heat  given  off  by  the  body 
measured,  the  amount  of  work  done  measured,  and  the  air 
going  in  and  coming  out  analyzed.  It  is  provided  with  a 
telephone,  so  that  the  subject  can  communicate  with  the 
outside  without  opening  the  box. 

Men  have  lived  in  this  box  for  from  3  to  12  days,  and 
during  all  this  time  accurate  analyses  have  been  made  of 
all  food  and  air  used,  all  work  done  has  been  measured, 
and  all  changes  in  the  weight  of  the  body  determined.  The 
effect  of  different  diets,  and  the  amount  of  food  necessary 
to  keep  the  body  in  condition,  have  been  determined. 

The  problem  has  been  attacked,  in  other  ways,  in  many 
countries,  until  we  can  now  estimate  closely  the  amount 
of  food  compounds  required  to  maintain  the  body  under 
different  conditions,  and  how  these  compounds  may  be 
obtained  from  different  combinations  of  foods. 

Balanced  ration.  A  diet  containing  the  proper  propor- 
tions of  fats,  carbohydrates,  and  protein,  to  maintain  the 
body  in  health,  is  called  a  balanced  ration.  In  the  army 
and  navy,  and  in  all  large  institutions,  an  effort  is  made  to 
provide  such  a  diet. 

You  will  find  in  the  tables  beginning  on  page  261  the 
analyses  of  the  different  foods  which  we  eat.  From  these 
you  can  calculate  whether  your  diet  is  properly  balanced. 

According  to  recent  experiments  by  Professor  Chittenden, 
of  Yale  University,  the  ordinary  man  weighing  160  pounds, 
and  doing  a  moderate  amount  of  work,  requires  2  oz.  of 
available  protein  per  day  and  enough  of  the  fuel  foods  (fats 
and  carbohydrates)  to  make  the  total  fuel  value  of  the  food 
consumed  2500-3000  Calories. 

Another  way  of  stating  this  fact  is :    -$$  of  an  ounce  of 


FOODS  259 

protein  is  required  for  each  pound  a  person  weighs,  and 
enough  of  the  fuel  foods  in  addition  to  make  up  a  total  of 
2500-3000  Calories  per  day. 

The  food  requirements  of  the  body  vary  with  the  amount 
of  work  done.  The  energy  requirement  which  should  be 
met  with  fats  and  carbohydrates  varies  almost  proportion- 
ally with  the  amount  of  work  done,  while  the  protein 
requirement  remains  nearly  constant.  These  statements 
apply  to  adults. 

Disadvantage  of  excessive  protein.  The  great  fault  with 
our  American  dietary  is  that  it  contains  too  much  protein. 
Protein  eaten,  but  not  required  by  the  body,  is  mainly 
broken  down  and  excreted  by  the  kidneys  as  uric  acid  and 
other  poisonous  substances.  This  is  not  only  a  waste,  but 
throws  too  much  of  a  strain  on  the  kidneys,  and  leads  to 
various  diseases. 

Ration  for  growing  boys  and  girls.  A  growing  child 
requires  more  food  in  proportion  to  his  weight  than  an  adult, 
as  is  explained  by  Frank  A.  Rexford  in  the  text  of  his  "  A 
One-Portion  Food  Table." 

"  Boys  and  girls  of  school  age  present  many  difficulties 
in  the  way  of  rational  feeding.  Their  needs  are  more  in 
proportion  to  their  size  and  weight  than  those  of  adults. 
They  must  have  building  stuff  (protein)  enough  to  keep  them 
in  repair,  and  in  addition  to  this  they  must  have  a  goodly 
amount  of  this  material  to  grow  on,  for,  if  they  are  normal 
and  healthy,  they  are  continuously  adding  new  tissues  to 
their  bodies.  They  must  also  have  a  generous  supply  of 
energy  stuffs  because  of  their  many  activities.  We  allow 
the  average  growing  child  2  to  2\  ounces  of  protein  per  day 
and  enough  of  the  fuel  stuffs  (fat  and  carbohydrates)  to 
bring  the  fuel  value  to  2000-3000  Calories  according  to 

WEED    CHEMISTRY 17 


260  CHEMISTRY   IN   THE    HOME 

his  activity.  A  boy  on  the  football  team  requires  more 
energy  stuff  than  the  girl  whose  chief  exercise  consists  in 
playing  the  piano.  The  tendency  of  most  children  is  to  eat 
nearly  double  the  amount  of  protein  they  need  and  rather 
less  of  the  fat  and  carbohydrates." 

Condiments.  There  are  certain  adjuncts  to  a  meal  that 
are  widely  used,  but  contain  little  nutriment.  These  are 
condiments  and  spices,  as  mustard,  pepper,  catsup,  and 
sauces.  They  may  be  useful,  however,  because  they  stimu- 
late a  jaded  appetite,  and  increase  the  secretion  of  the 
digestive  juices.  The  beverages,  as  tea  and  coffee,  act  as 
stimulants,  but  have  no  nutritive  value.  The  use  of  all 
these  is  best  kept  at  a  minimum. 

Use  of  the  one-portion  food  table.  Knowing  the  require- 
ments of  your  body,  you  can  use  the  food  tables1  on  the 
following  pages  to  plan  a  balanced  dietary  that  will  give  you 
the  proper  amount  of  protein,  and  Calories  enough  to  main- 
tain your  body  at  its  highest  efficiency.  If  you  will  note  down 
for  a  few  days  the  amount  of  food  that  you  eat,  you  can 
readily,  by  using  this  table,  determine  whether  your  diet  is  a 
suitable  one.  If  it  is  not,  you  will  do  well  to  correct  it. 

On  page  271  is  given  a  child's  dietary  taken  at  random  from 
several  thousands.  The  figures  giving  the  values  of  the 
different  "  food  stuffs  "  and  the  fuel  value  were  copied  from 
the  table  and  totaled.  The  results  show  that  the  child 
was  getting  3.77  ounces  of  protein  per  day  and  enough  fat 
and  carbohydrates  to  make  the  fuel  reach  2890  Calories. 
In  this  particular  case  the  child  was  instructed  to  lower 

1  These  food  tables  were  computed  and  arranged  in  a  convenient 
form  by  Mr.  Rexford.  He  has  worked  for  several  years  with  the 
students  of  the  Erasmus  Hall  High  School  and  determined  the 
weight  of  the  ordinary  helping  of  the  common  foods. 


FOODS 


261 


the  protein  total  to  2.5  ounces  and  the  fuel  total  to  something 
between  2000  and  2500  Calories  without  diminishing  the 
number  of  dishes.  The  modified  dietary  is  shown  on  page 

271. 

FOODS  PRIMARILY   OF  PLANT   ORIGIN 


o 
55 

OF  THIS  THE  BODY  CAN  USE 

fc  * 

<  o  ° 

&  s 

^fflZg 

FOOD  AS  WE  EAT  IT 

I? 

Muscle 
Builder 

For  Heat  and  Energy 

lisl 

s  " 

Carbohy- 

0 O  W  H 
PH  EH  fc  < 

5 

P3 

Protein 

Fat 

drates 
(Starch 

j£3*E 

o 

and  Sugar) 

H  £  " 

Beverages 

Ounces 

Ounces 

Ounces 

Ounces 

Calories 

Cocoa 

5. 

.11 

.33 

.19 

123. 

Coffee     (cream 

and        sugar 

only)    .     .     . 

.75 

.01 

.17 

.27 

53. 

Lemonade  .     . 

5.5 



— 

.66 

78.1 

Orange  juice    . 

5. 





.65 

75.5 

Bread 

Biscuit,  cream 

2.33 

2 

.2 

1. 

203.9 

home  made 

2. 

.17 

.05 

1.1 

162.5 

soda   . 

2. 

.19 

.27 

1.05 

216.3 

Bread,  corn 

2. 

.16 

.09 

.93 

150.6 

gluten      .     . 

2. 

.18 

.03 

.99 

145. 

graham    . 

2. 

.18 

.04 

1.04 

151.3 

home  made 

2 

.18 

.03 

1.07 

153.1 

plain  rolls     . 

2! 

.19 

.08 

1.2 

182.08 

rye      ... 

2. 

.23 

.01 

.71 

148.4 

whole  wheat 

2 

.19 

.02 

.99 

142.5 

zwieback 

l! 

.1 

.1 

.74 

123.2 

and  butter    . 

2.5 

.22 

.48 

1.18 

275. 

Buns,  hot  cross 

1.25 

.1 

.06 

.6 

99.6 

Crackers, 

graham    .     . 

1. 

.1 

.09 

.74 

122.2 

oatmeal    . 

1. 

.12 

.11 

.69 

123.1 

pretzels   .     . 

1. 

.1 

.04 

.73 

106.3 

sal  tines    .     . 

1. 

.11 

.13 

.69 

125.3 

soda    . 

1. 

.1 

.09 

.73 

120.3 

Toast,  cream 

5. 

.2 

.56 

.6 

238.5 

Toast,  dry  . 

5. 

.06 

.008 

.3 

44.4 

262  CHEMISTRY   IN   THE   HOME 

FOODS  PRIMARILY   OF  PLANT   ORIGIN  — Continued 


1 

OF  THIS  THE  BODY  CAN  USE 

% 

FOOD  AS  WE  EAT  IT 

H 

Muscle 
Builder 

For  Heat  and  Energy 

iigj 

9  S 

Carbohy- 

£ °*  « 

K 

Protein 

Fat 

drates 
(Starch 

2  9    W 

0 

and  Sugar) 

H  £ 

Cake 

Ounces 

Ounces 

Ounces 

Ounces 

Calories 

Chocolate, 

layer  .     .     . 

2.5 

.14 

.2 

1.6 

256.8 

Charlotte  russe 

4.25 

.26 

.56 

2.39 

395.2 

Coffee     .     .     . 

2. 

.14 

.15 

1.28 

203.1 

Cookies, 

molasses 

1.75 

.13 

.16 

1.32 

209. 

sugar  .     .     . 

1.5 

.11 

.15 

1.1 

180. 

Doughnuts 

1.75 

.12 

.37 

.93 

218.8 

Frosted  .     .     . 

2. 

.12 

.18 

1.3 

211.9 

Fruit       .     .     . 

2. 

.12 

.22 

1.28 

220. 

Gingerbread     . 

2 

.12 

.18 

1.37 

208.8 

Jelly  roll      .     . 

3. 

.15 

.12 

2.19 

301.2 

Lady  fingers     . 

.5 

.04 

.03 

.35 

52.7 

Macaroons 

1. 

.07 

.15 

.65 

123.4 

Nut         ... 

2.5 

.2 

.54 

1.36 

324.4 

Sponge   .     .     . 

1.5 

.09 

.16 

.9 

168.3 

Cereals 

Corn  flakes 

.75 

.07 

.003 

.59 

77.6 

Farina    . 

4. 

.44 

.06 

2.98 

421.2 

Hominy       .     . 

4. 

.08 

.01 

.72 

95. 

Oatmeal       .     . 

4.25 

.13 

.02 

.49 

76.5 

Puffed  rice 

.5 

.04 

— 

.4 

50.9 

Rice  .... 

4. 

.11 

.001 

.96 

124.72 

Shredded 

wheat  (2)     . 

2. 

.21 

.03 

1.56 

212.5 

Wheat  flakes   . 

.75 

.1 

.01 

.56 

79.2 

Fruit 

Apple,  baked  . 

3.25 

.02 

.02 

.78 

98.5 

Apple,  fresh 

5.5 

.02 

.02 

.78 

99.6 

Apple,  sauce    . 

3.5 

.01 

.03 

1.3 

76.1 

Bananas      .     . 

3.5 

.05 

.02 

.77 

100.8 

FOODS 


263 


FOODS  PRIMARILY   OF   PLANT   ORIGIN  —  Continued 


o 

OF  THIS  THE  BODY  CAN  USE 

?  « 

E 

o  2.  %  0j 

o  £] 

Muscle 
Builder 

^or  Heat  and  Energy 

IBS! 

FOOD  AS  WE  EAT  IT 

2  « 

o  o  w  ^ 

H  •< 

Carbohy- 

*\ 

K 

Protein 

Fat 

drates 
(Starch 

gSgw 

0 

and  Sugar) 

^£ 

Fruit  (cont'd) 

Ounces 

Ounces 

Ounces 

Ounces 

Calories 

Cherries      .     . 

2. 

.03 

.01 

.44 

45.6 

Currants      .     . 

3. 

.04 

— 

.37 

50.1 

Cranberries 

3. 

.01 

.02 

.3 

40.3 

Dates      .     .     . 

1.75 

.04 

.05 

.59 

177.6 

Figs   .     ._    .     . 

2 

.09 

.01 

1.5 

184.4 

Grapefruit 

3J5 

.03 

.01 

.37 

49.5 

Grapes    .     .     . 

5. 

.05 

.06 

.71 

104.5 

Huckleberries  . 

3. 

.02 

.02 

.5 

64.6 

Lemons 

1. 

.01 

— 

.08 

13.2 

Olives,  green    . 

1.33 

.01 

.37 

.15 

116.3 

Olives,  ripe 

1.33 

.02 

.33 

.06 

100.1 

Oranges        .     . 

5. 

.04 

.01 

.58 

75. 

Peaches,  cooked 

3.5 

.04 

.04 

.54 

73.2 

Pineapple, 

canned     .     . 

3.25 

.013 

.227 

1.18 

145.21 

fresh    . 

4. 

.016 

.012 

.38 

52.48 

Prunes,  cooked 

3.75 

.03 

.004 

.85 

103.1 

Raspberries, 

black  .     .     . 

4. 

.07 

.04 

.5 

77.2 

red      .     .     . 

3.5 

.04 

— 

.44 

55.7 

Rhubarb 

2.5 

.01 

.01 

.57 

67. 

Strawberries, 

fresh   .     .     . 

4.25 

.04 

.03 

.31 

48.5 

Jelly 

Cherry    . 

1. 

.01 

— 

.21 

90.9 

Cranberry  .     . 

2. 

.01 

.01 

.85 

102.2 

Currant 

1. 

.01 

— 

.77 

91.3 

Orange    . 

2.75 

— 

— 

.85 

100.1 

Peach     .     .     . 

3.5 

.02 

.05 

.74 

98.4 

Miscellaneous 

Brown  gravy   . 

2.25 

.03 

.26 

.07 

81.2 

Hash,  beef  .    . 

2.2 

.26 

.27 

.32 

114.3 

264 


CHEMISTRY   IN   THE   HOME 


FOODS  PRIMARILY   OF  PLANT   ORIGIN  —  Continued 


0 

OF  THIS  THE  BODY  CAN  USE 

fc  * 

<  o  o 

FOOD  AS  WE  EAT  IT 

IS 

Muscle 
Builder 

For  Heat  and  Energy 

O    O    W    EH 

H  < 

Carbohy- 

*s 

Protein 

Fat 

drates 
(Starch 

3  w  SW 

o 

and  Sugar) 

H£ 

Miscellaneous  (cont'd] 

Ounces 

Ounces 

Ounces 

Ounces 

Calories 

Macaroni    . 

2.75 

.36 

.02 

2.00 

286.2 

Macaroni  with 

cheese      .     . 

2.75 

.26 

.16 

.42 

122.4 

Mayonnaise 

dressing 

(cooked) 

1.25 

.07 

.32 

.03 

'    96. 

Olive  oil 

(tablespoon) 

.33 

— 

.33 

— 

88. 

Salad    dressing 

(French)       . 

.5 

— 

.74 

.02 

100.4 

Nuts 

Almonds 

.25 

.05 

.14 

.04 

47.8 

Beech     .     .     . 

.5 

.11 

.29 

.07 

97. 

Brazil      .     .     . 

.5 

.09 

.33 

.04 

103. 

Butter    .     .     . 

.5 

.14 

.31 

.02 

99.9 

English 

walnuts   . 

.5 

.08 

.32 

.08 

103.4 

Filberts       .     . 

.5 

.08 

.33 

.07 

103.7 

Hickory 

.5 

.08 

.34 

.06 

105.5 

Peanuts       .     . 

.5 

.13 

.19 

.12 

80.1 

Pecan     .     .     . 

.5 

.06 

.36 

.7 

108.9 

Pickles 

Cucumber 

1.25 

.006 

.004 

.03 

5.4 

Mixed     .     .     . 

1. 

.01 

.004 

.04 

6.9 

Spiced    .     .     . 

1. 

.004 

.001 

.21 

24.7 

Pie 

Apple     .     .     . 

4.5 

.29 

.31 

1.44 

282.8 

Blueberry    .     . 

3.87 

.15 

.19 

1.5 

237. 

Cream    .     .     . 

4. 

.18 

.46 

2.05 

380. 

Custard 

4. 

.17 

.25 

1. 

207.2 

FOODS 


265 


FOODS  PRIMARILY   OF   PLANT   ORIGIN  — Continued 


| 

OF  THIS  THE  BODY  CAN  USE 

<  o  Q 

0  H 

i 

fc          "**    w 

HW 

Buifder      For  Heat  and  Ener^ 

2  §  g  % 

FOOD  AS  WE  EAT  IT 

h 

' 

|    0    §    EH 

H  •< 

Carbohy- 

P~* ^  M  a 

03 

Protein 

Fat 

drates 
(Starch 

£  w  5 

o 

and  Sugar) 

Pie  (cont'd) 

Ounces 

Ounces 

Ounces 

Ounces 

Calories 

Coconut 

cream      .     . 

3.87 

.23 

.46 

1.04 

235.2 

Lemon    . 

4. 

.14 

.4 

1.4 

297.2 

Mince     .     .     . 

5. 

.65 

.42 

1.51 

362. 

Pumpkin     .     . 

5. 

.15 

.15 

1. 

177. 

Raisin     . 

5. 

.15 

.56 

2.36 

439.5 

Squash   .     .     . 

5. 

.22 

.42 

1.08 

265.5 

Pudding 

Blanc     mange 

(chocolate) 

3.5 

.1 

.3 

.49 

148.8 

Bread     ...        3.5 

.19 

.42 

.57 

131.6 

Custard       .     .        3.25 

.16 

.16 

.35 

102.4 

Date       .     .     . 

2.5 

.15 

.23 

1.4 

243. 

Fig     .... 

2.75 

.11 

.17 

.82 

150.4 

Floating  island 

3. 

.15 

.05 

.55 

118.8 

Indian  meal    . 

3.25 

.18 

.16 

.89 

165.5 

Rice       .     .     . 

3.25 

.12 

.28 

.55 

149.5 

Snow      .     .     . 

2.5 

.1 

.07 

.35 

75.9 

Tapioca 

3.25 

.11 

.1 

.92 

146.3 

and  apple     . 

3.25 

.01 

.003 

.95 

112.4 

Salad 

Date  and  apple 

2.25 

.05 

.05 

.87 

121.7 

Date  and 

walnut     .     . 

1.25 

.63 

.16 

.62 

124.1 

Egg  mayon- 

naise . 

2.25 

.26 

.25 

.02 

100.1 

Fruit       .     .     . 

2.25 

.04 

.02 

.52 

70.4 

Potato    .     .     . 

2.25 

.09 

.22 

.29 

102.1 

String  bean 

L75 

.01 

.33 

.04 

95.7 

Tomato  (with 

mayonnaise) 

4. 

.06 

.16 

.15 

67.6 

266  CHEMISTRY   IN   THE    HOME 

FOODS  PRIMARILY   OF  PLANT   ORIGIN  —  Continued 


1 

OF  THIS  THE  BODY  CAN  USE 

<J  o  Q 

FOOD  AS  WE  EAT  IT 

£ 

upq  *  05 
o  H  *  1 

Muscle 
Builder 

For  Heat  and  Energy 

H  * 

Carbohy- 

(2° *  | 

i 

Protein 

Fat 

drates 
(Starch 

3  w  5 

i      o 

and  Sugar 

H  P 

Soup                                  Ounces 

Ounces     i    Ounces 

Ounces 

Calories 

Bean       .     .     . 

4.75 

.38 

.07 

1. 

182.8 

Cream  of 

celery       .     . 

4.75 

.11 

.34 

.17 

124.8 

corn    .     .     . 

4.75 

.14 

.33 

.4 

152. 

Chicken       .     . 

4.75 

.19 

.01 

.1 

31.3 

Consomme 

4.75 

.1 

— 

.02 

16. 

Clam    chowder 

4.75 

.09 

.04 

.33 

60. 

Lentil     .     .     . 

4.75 

.23 

.25 

.48 

161.5 

Oxtail     .     .     . 

4.75 

.2 

.06 

2 

65. 

Potato    .     .     . 

4.75 

ill 

.03 

.37 

146.8 

Tomato       .     . 

4.75 

.13 

.12 

.33 

91.2 

Vegetable 

(canned)  .     . 

4.75 

.13 

— 

.02 

192.8 

Sugars 

Candy, 

caramel    . 

1. 

.05 

— 

.81 

100.4 

chocolate 

1. 

.01 

.01 

.73 

90. 

Chocolate    . 

almonds 

1.5 

.06 

.15 

.95 

160. 

Honey    .     .     . 

1.63 

.1 

— 

1.32 

155.2 

Maple  sirup 

1.25 

— 

— 

.89 

103.9 

Maple  sugar    . 

1. 

— 

— 

.83 

96.6 

Sugar     (granu- 

lated or  loaf) 

.25 

— 

— 

.25 

27. 

Vegetables 

Asparagus    (on 

toast)       .     . 

4. 

.18 

.4 

.64 

202.8 

Beans,  baked  . 

3.25 

.31 

.18 

1.08 

182. 

kidney 

3.25 

.22 

.65 

.6 

97.5 

string       .     . 

4. 

.69 

.61 

.21 

48.72 

Beets      .     .     . 

2.25 

.05 

.002 

.15 

26.1 

FOODS 


267 


FOODS  PRIMARILY   OF  PLANT   ORIGIN  —  Continued 


1 

OF  THIS  THE  BODY  CAN  USE 

5g 

r      ^ 

°  rQ  £  02 

sg 

§w 

Muscle 
Builder 

For  Heat  and  Energy 

ias! 

FOOD  AS  WE  EAT  IT 

Is 

0  0  H  frj 

II 

Carbohy- 

'I 

Protein 

Fat 

drates 
(Starch 

3  g  5 

0 

and  Sugar) 

Vegetables  (cont'd) 

Ounces 

Ounces 

Ounces 

Ounces 

Calories 

Cabbage,  boiled 

4. 

.03 

.09 

.16 

35.2 

Carrots 

3.75 

.04 

.02 

.35 

49.2 

Cauliflower 

4. 

.07 

.02 

.2 

35. 

Celery     .     .     . 

1. 

.01 

.003 

.04 

5.5 

Corn,  canned 

2.75 

.08 

.03 

.52 

74.25 

Cucumbers 

2 

.03 

.004 

.06 

10. 

Egg  plant    .     . 

L5 

.09 

.15 

'.48 

106.5 

Lettuce        .     . 

1. 

.01 

— 

.03 

7. 

Mushrooms 

1, 

.04 

.01 

.07 

13.1 

Onions,    boiled 

2.5 

.03 

.11 

.13 

26.3 

creamed 

3. 

.04 

.15 

.15 

65.7 

scalloped 

3. 

.08 

.27 

.09 

73.9 

Parsnips, 

creamed 

3. 

.03 

.07 

.44 

79. 

browned 

3. 

.05 

.13 

.29 

75.6 

Peas,  canned    . 

3. 

.09 

.09 

.54 

66.6 

green       .     . 

3. 

.13 

.1 

.2 

103.2 

Potatoes,  sweet 

3. 

.09 

.06 

1.26 

173.4 

Potatoes, 

baked 

3. 

.1 

.01 

.68 

98.1 

boiled      .     . 

3. 

.08 

.01 

.73 

82.8 

browned 

3.25 

.11 

.06 

.82 

123.5 

mashed    . 

3.25 

.09 

.26 

.68 

100.4 

Radishes     .     . 

1. 

.01 

— 

.05 

8.5 

Spinach       .     . 

3. 

.06 

.12 

.09 

16.3 

Squash,  winter 

(baked)    .     . 

.3.75 

.05 

.01 

.33 

50.4 

Succotash    . 

3. 

.11 

.03 

.56 

78. 

Tomatoes, 

sliced       .     . 

4. 

.04 

.04 

.18 

26.8 

stewed 

2.5 

.03 

— 

.08 

16.4 

Turnips, 

mashed    .     . 

4. 

.02 

.11              .11 

24.4 

268  CHEMISTRY   IN   THE    HOME 

FOODS  PRIMARILY  OF  ANIMAL   ORIGIN 


0 

OP  THIS   THE   BODY   CAN  USE 

fc  ^ 

.  S 

0    °    §    32 

FOOD  AS  WE  EAT  IT 

o£ 

Muscle 
Builder 

71  or  Heat  and  Energy 

\l  |  J 

—  — 

Q       Q      £3       H 

Carbohy- 

PH H  fc  < 

^1 

Protein 

Fat 

drates 
(Starch 

2Sg« 

0 

and  Sugar) 

H£ 

Beef 

Ounces 

Ounces 

Ounces 

Ounces 

Calories 

Chuck    .     .     . 

3. 

.57 

.04 

— 

172.5 

Corned  . 

2. 

.21 

.52 

— 

174.2 

Dried      .     .     . 

1. 

.26 

.07 

— 

49.4 

Flank      .     .     . 

2.25 

.44 

.47 

— 

176.4 

Heart      .     .     . 

1. 

.16 

.2 

— 

72.5 

Liver      .     .     . 

2. 

.41 

.09 

.03 

75.6 

Round    . 

2.25 

.43 

.29 

— 

125.2 

Sirloin    . 

2.25 

.37 

.36 

— 

137.1 

Sweetbreads     . 

2. 

.33 

.24 

— 

103.4 

Tongue, 

pickled    .     . 

2. 

.21 

.41 

— 

138. 

Tripe      .     .     . 

3. 

.38 

.04 

.01 

60.4 

Dairy  Products 

Butter    .     .     . 

.5 

.05 

.43 

— 

112.5 

Buttermilk 

6. 

.18 

.03 

.29 

61.9 

Cheese, 

cottage    . 

2. 

.31 

.09 

.09 

74.6 

full  cream     . 

1. 

.26 

.34 

.02 

122.4 

Neuchatel    . 

2. 

.37 

.55 

.03 

191.3 

pineapple 

2! 

.6 

.78 

.05 

280.6 

Swiss  .     .     . 

1. 

.22 

.35 

.01 

125.6 

Condensed  milk 

(sweetened) 

.25 

.02 

.02 

.14 

23.8 

(unsweet- 

ened) . 

.25 

.02 

.02 

.03 

10.6 

Cream, 

(tablespoon) 

.5 

.01 

.17 

.02 

26. 

whipped 

.5 

.13 

.09 

.05 

31.1 

Ice1  cream   . 

2. 

.05 

.1 

.91 

134.7 

Milk,  skimmed 

6.5 

.22 

.02 

.33 

71.3 

whole      .     . 

6.               .19 

.24 

.3 

123.6 

Oleomargarine 

.5 

.4 

110.2 

FOODS 


269 


FOODS  PRIMARILY   OF  ANIMAL   ORIGIN  — Continued 


0 

g 

Or  THIS  THE  BODY  CAN  USE 

£  ^ 

El 

<-i  .5  ^  t/j 

FOOD  AS  WE  EAT  IT 

rf 

Muscle 
Builder     i 

For  Heat  and  Energy 

o  w  ^z 

2  « 

Q      Q      W      E^ 

»  •< 

Carbohy- 

PL, H  £  ^ 

^§ 

Protein 

Fat 

drates 
(Starch 

s!sw 

0 

andSugar 

^  £ 

Eggs 

Ounces 

Ounces 

Ounces 

Ounces 

Calories 

Boiled  (2)    .     . 

3.75 

.49 

.45 

—  • 

179.1 

Omelet    .     .     . 

4. 

.48 

.88 

.03 

296. 

Poached      .     . 

1.25 

.18 

.15 

— 

60.4 

on  toast  .     . 

2.5 

.3 

.17 

.29 

144.4 

Scrambled 

2. 

.24 

.17 

.03 

78.5 

Uncooked  (2) 

3.75 

.49 

.45 

— 

179.1 

Fish 

Blue        .     .     . 

5. 

1.3 

.23 

— 

209.4 

Cod    .... 

5. 

.32 

.02 

— 

101.6 

Halibut,    steak 

3. 

.56 

.16 

— 

105.9 

Herring 

.5 

.56 

.16 

— 

105.9 

Salmon, 

canned     .     . 

2. 

.44 

.24 

— 

114.1 

Sardines 

1. 

.23 

.19 

— 

78.1 

Shad       .     .     . 

2.25 

.42 

.22 

— 

104.9 

Trout    (brook) 

1.75 

.33 

.36 

— 

135.9 

Fowl 

Chicken 

(broilers) 

3.5 

.75 

.09 

— 

110.5 

fricasseed 

3.5 

.62 

.4 

.08 

187. 

Goose 

2.75 

.43 

.98 

— 

312.1 

Turkey  .     .     . 

1.25 

.26 

.26 

— 

104. 

Lamb 

Chops     .     .     . 

2. 

.43 

.59 

— 

210. 

Kidney  stew    . 

4. 

.72 

.2 

.08 

150. 

Leg    .... 

3.5 

.67 

'.44 

— 

194.3 

Mutton 

Leg    .... 

2.5 

.62 

.51 

— 

108. 

270 


CHEMISTRY   IN   THE   HOME 


FOODS  PRIMARILY   OF  ANIMAL   ORIGIN  —  Continued 


o 
g 

OF  THIS  THE  BODY  CAN  USE 

jjl|e 

FOOD  AS  WE  EAT  IT 

ll 

Muscle 
Builder 

For  Heat  and  Energy 

M   PH 

Carbohy- 

£  g  §| 

^1 

Protein 

Fat 

drates 
(Starch 

Si|5W 

o 

and  Sugar) 

H  £ 

Pork 

Ounces 

Ounces 

Ounces 

Ounces 

Calories 

Bacon 

1. 

.1 

.66 

188.6 

Chops 

3. 

.47 

.95 

—  . 

309. 

Ham  croquettes 

2. 

.3 

.24 

.11 

111.2 

Ham,  lean  . 

2.25 

.49 

.55 

— 

203.2 

Sandwiches 

Cheese    .     .     . 

3.25 

.41 

.49 

1.2 

314.2 

Egg   .... 

4. 

.4 

.37 

1.19 

279.7 

Ham 

3.5 

.33 

.48 

1.19 

302.7 

Jelly        .     .     . 

2. 

.01 

.01 

.85 

102.2 

Lamb 

4. 

.53 

.48 

1.1 

316. 

Lettuce  and 

mayonnaise 

3.5 

.22 

.24 

1.21 

214.2 

Roast  beef 

3.5 

.39 

.39 

1.19 

275.8 

Sardine        .     . 

3.5 

.44 

.35 

1.19 

279.6 

Sausages 

Bologna      .     . 

2. 

.37 

.35 

.01 

136.8 

City        ... 

2. 

.35 

.48 

— 

172.5 

Country      .     . 

2. 

.56 

.8 

— 

278.1 

Frankfurters    . 

2 

.39 

.37 

.02 

141.6 

Shellfish 

Clams     ... 

3.75 

.24 

.02 

— 

32.2 

Lobster        .     . 

2, 

.32 

.04 

— 

47.6 

Oysters 

3.5 

.21 

.04 

— 

36.4 

Scallops       .     . 

2. 

.29 

— 

.07 

43.1 

Veal 

Breast      (lean) 

2.5 

.38 

.25 

— 

104.8 

Cutlets   .     .     . 

3.5 

.7 

.26 

— 

152. 

Leg    .... 

2.5 

.65 

.1 

— 

104. 

Liver      .     .     . 

3. 

.56 

.17 

— 

107.1 

FOODS 
ORDINARY  DAILY   DIETARY 


271 


FOOD  FOR  ONE  DAY 

OF  THIS  THE  BODY  CAN  USE 

THIS  POR- 
TION CAN 

YIELD    TO 

THE  BODY  IN 
ENERGY  AND 
EEAT  UNITS 

Protein 

Fat 

Carbohy- 
drates 
(Starch  and 
Sugar) 

Breakfast 
Oranges      

.04 
.01 
.22 

.48 

1.17 
.04 
.01 

.43 
.09 
.09 
.01 
.60 
.10 
.29 
.19 

.01 
.17 

.48 
.88 

1.17 
.01 
.01 

.59 
.26 
.09 

.78 
.09 
.31 
.24 

.58 
.27 
1.18 
.03 

3.57 

.58 
.73 

.68 
.54 
.03 
.09 
.73 
1.44 
.30 

75. 
53. 
275. 
296. 

827.4 
75. 
90. 

210. 
103.4 
66.6 

280.6 

120.3 

287.8 
123.6 

Coffee    
Bread  and  butter    .     . 
Omelet       

Lunch 
3  Beef  sandwiches 
Orange       .               . 

Chocolate  candy 

Dinner 
Lamb  chops        .     .     . 
Potatoes,  mashed     . 
Peas      .... 

Lettuce      
Pineapple  cheese 
Crackers,  soda    .     .     . 
Apple  pie        .... 
Milk      

Total 

3.77 

5.09 

10.75 

2890.7 

MODIFIED   DIETARY 


Breakfast 
Oranges      

04 

01 

58 

75 

Rice 

11 

001 

96 

124  72 

Cocoa    . 

11 

33 

19 

123 

Dry  toast  

06 

008 

3 

444 

Butter 

05 

43 

112  5 

Lunch 
Bean  soup      .... 
Lettuce    and    mayon- 
naise sandwiches 
Dates    .... 

.38 

.44 
04 

.07 

.48 
05 

1. 

2.42 

59 

182.8 

428.4 
177  6 

272 


CHEMISTRY   IN   THE   HOME 
MODIFIED  DIETARY  —  Continued 


OF  THIS  THE  BODY  CAN  USE 

THIS  POR- 
TION  CAN 

FOOD  FOB  ONE  DAY 

Protein 

Fat 

Carbohy- 
drates 
(Starch  and 
Sugar) 

YIELD    TO 

THE  BODY  IN 
ENERGY  AND 
HEAT  UNITS 

Dinner 

Cream  of  celery  soup 

.11 

.34 

.17 

124.8 

Breast  of  veal     .     .     . 

.38 

.25 

— 

104.8 

Baked  potatoes        .     . 

.1 

.01 

.26 

98.1 

Green  peas     .... 

.13 

.1 

.2 

103.2 

Salad,  string  bean 

.01 

.33 

.04 

95.7 

Bread  and  butter    .     . 

.22 

.48 

1.18 

275. 

Pudding,  floating  island 

.15 

.05 

.55 

118.8 

Whole  milk    .... 

.19 

.24 

.3 

123.6 

3  O'Cloek  Lunch 

Lemonade      .... 

— 

— 

.66 

78.1 

Total      . 

2.52 

3.179 

9.40 

2390.52 

Family  food  table.1  Another  food  table  by  Mr.  Rexford 
refers  to  the  analysis  of  food  as  bought  in  the  market.  By 
keeping  the  family  market  lists  for  a  week,  and  computing 
the  nourishment  in  the  foods  bought  by  this  table,  you  can 
compute  the  actual  nourishment  obtained  for  the  money 
expended.  The  use  of  this  table  will  lead  to  economy  in 
buying  foods. 

In  the  study  of  this  table  a  knowledge  of  the  use  and  value 
of  each  of  the  different  foodstuffs,  as  given  in  "A  One-Por- 
tion Food  Table,"  is  presupposed.  Up  to  this  time  our  study 
of  nutrition  has  been  confined  to  the  consideration  of  the 
needs  of  the  individual  and  of  food  as  eaten.  When  we  come 

1  Separate  copies  of  Rexford's  food  tables,  classroom  and  home 
record  blanks,  can  be  obtained  from  Educational  Equipment  Co., 
70  Fifth  Ave.,  New  York,  N.  Y. 


FOODS 


273 


to  buying  food  the  proposition  is  a  little  different.  We  do 
not  buy  food  by  the  portion ;  we  buy  it  as  it  is  sold  in  the 
market.  The  analyses  here  given  are  therefore  in  most 
cases  computations  from  government  bulletins  and  are  for 
quantities  of  different  foods  in  just  the  condition  we  buy 
them.  That  is,  meat  with  the  bone,  lobster  with  the  shell, 
peas  with  the  pods,  nuts  with  the  shell,  etc. 

The  following  family  market  list  shows  the  food  bought 
for  seven  people  for  one  week.  Work  it  out,  and  answer 
the  following  questions : 

1.  Is  this    family  of    seven    people    getting    the    proper 
amount  of  protein  ? 

2.  Is  its  fuel  value  well  regulated  ? 

3.  Is  this  an  economical  or  an  extravagant  weekly  list? 


FAMILY  MARKET   LIST 


1  head  lettuce 

3  baskets  potatoes 

2  qt.  onions 

3  bunches  celery 
6  qt.  spinach 

1  hd.  cabbage 

3  cans  peaches 

2  doz.  bananas 

4  qt.  apples 

1  doz.  oranges 
1  Ib.  coffee 
i  Ib.  tea 
1  can  cocoa 
1  Ib.  walnuts 
4  Ib.  butter 
4  doz.  eggs 

NOTE.  —  It  is  not  necessary  to  total  the  fat  and  carbohydrate 
columns,  as  their  value,  in  the  main,  is  given  in  the  Calorie  column. 
It  is  well  to  record  them,  however,  in  order  to  keep  in  mind  the 
proportions  of  fuel  ingredients  found  in  the  different  foods,  so  that 
the  fuel  value  may  be  controlled  by  increasing  or  curtailing  them, 
as  the  case  demands. 


3^  Ib.         pork,  loin            ( 
3    Ib          lamb,  leg 
|    Ib.         dried  beef 

&  24c 
'  22c 
'  25c 

1    Ib.         codfish,  salt 

'  18c 

1\  Ib.         beef,  sirloin 
1    Ib.         bacon 

'  28c 
'  26c 

1    Ib.         sausage 
10  Ib.         beef,   roast 

'  20c 
'  25c 

10  loaves  bread,  white 

'  lOc 

5    loaves  bread,  graham 
4    doz.      rolls 

'  lOc 
'  lOc 

1    pkg.      oatmeal 
2    Ib.         crackers,  soda 

'  lOc 
'  15c 

1    pkg.      tapioca 
7    Ib.         sugar,  gran. 
21  qt.        milk 

'  lOc 
'  36c 
'  9c 

lOc 
20c 
15c 
12c 
15c 
6c 
25c 
15c 
16c 
40c 
30c 
50c 
40c 
23c 
37c 
40c 


274 


CHEMISTRY   IN   THE   HOME 


This  work  has  value  only  when  it  is  applied.  It  is  desir- 
able that  each  family  in  the  community  work  out  a  weekly 
market  list  and  compare  notes.  This  can  be  done  by  keep- 
ing account  in  each  case  of  what  is  bought  and  the  price 
paid.  A  tabulation  of  the  results  will  show :  (a)  compara- 
tive cost  of  the  same  foods  in  different  parts  of  the  town; 
(b)  whether  or  not  the  family  is  being  approximately  well 
nourished;  (c)  whether  or  not  the  family  is  getting  good 
value  in  nourishment  for  the  money  expended  each  week. 

FAMILY  FOOD  TABLE 
FOODS  PRIMARILY  OF  PLANT  ORIGIN 


FOOD  AS  WE  BUY  IT 

NOURISHMENT  IN  THIS  FOOD 

fc  Q  Q 

IIP 

Muscle 
Builder 

For  Heat  and  Energy 

Protein 

Fat 

Carbohy- 
drates 
(Starch 
andSugar) 

Beverages 
Cocoa,  1  Ib.  can      .     .     . 
Coffee,  1  Ib  
Tea  1  Ib 

Pounds 
.22 
.00 
.00 

.07 
.06 
.10 
.07 
.07 
.08 

.10 
.12 
.10 
.11 
.10 

Pounds 
.28 
.00 
.00 

.08 
.01 
.04 
.01 
.01 
.01 

.09 
.11 
.04 
.13 
.09 

Pounds 
.38 
.00 
.00 

.58 
.39 
.60 
.40 
.40 
.37 

.73 
.69 
.73 
.69 
.73 

Calories 
2320 
0000 
0000 

1515 

908 
1470 
912 
912 
855 

1955 
1970 
1700 
2005 
1925 

Bread 
Buns,  1  doz.,  1  Ib.       .     . 
Graham,  5c.  loaf,  1  Ib. 
Rolls,  1  doz.,  1  Ib.       .     . 
Rye,  5c.  loaf,  12  oz.    . 
White,  5c.  loaf,  12  oz.      . 
Whole  Wheat,  12  oz.  loaf 

Crackers 
Graham,  1  Ib. 

Oatmeal   1  Ib 

Pretzels,  1  Ib.     .     . 

Saltines,  1  Ib 

Soda,  1  Ib.     .     .     . 

FOODS 
FOODS  PRIMARILY  OF  PLANT  ORIGIN  —  Continued 


275 


FOOD  AS  WE  BUY  IT 

NOURISHMENT  IN  THIS  FOOD 

Q 

fc  0  Q 

Q  8  *  * 
o  ^  & 

ft(  O  W  H 

Muscle 
Builder 

For  Heat  and  Energy 

Protein 

Fat 

Carbohy- 
drates 

(Starch 
and  Sugar) 

Cake 
Charlotte  russe,  1,  4.25  oz. 
Chocolate,   layer,   3|   Ib. 
Cookies,  molasses,  1  doz., 

19  ra. 

Pounds 
.02 
.20 

.07 

.05 
.05 
.06 
.06 
.02 
.07 
.06 

.19 
.15 
.22 

.08 

.09 
.12 

.22 
.32 
.45 
.09 
.24 
.09 
.38 
.76 
2.65 
.66 

Pounds 
.04 
.27 

.15 

.07 
.16 
.11 
.09 
.02 
.15 
.11 

.02 
.01 
.10 
.00 

.01 
.02 

.04 
.07 
.03 
.01 
.03 
.00 
.04 
.08 
.27 
.09 

Pounds 
.17 
2.10 

.65 

.55 
.40 
.64 
.63 
.18 
.65 
.66 

1.34 
1.38 
.93 
.79 

.56 
.75 

.27 
2.54 
2.50 
.56 
2.75 
.57 
2.62 
5.24 
18.32 
3.24 

Calories 
395 
5500 

1975 

1440 
1500 
1760 
1670 
422 
1975 
1795 

2949 
2888 
2558 
1630 

1275 
1680 

5607 
5722 
5775 
1233 
5705 
1245 
5740 
11480 
40180 
7956 

Cookies,  sugar,  1  doz.,  12 
oz  
Doughnuts,  1  doz.,  12  oz. 
Fruit,  1  Ib  
Gingerbread,  1  Ib. 
Lady  fingers,  1  doz.,  4  oz. 
Macaroons,  1  Ib.     . 

Knnntrp     1    Ib 

Cereals 
Farina,  1  box,  28  oz.  . 
Hominy,  1  box,  28  oz.      . 
Oatmeal,  1  box,  28  oz. 
RiW    1  Ib 

Shredded  wheat,    1   box, 
12  oz 

Wheat  breakfast  foods,  1 
Ib. 

Flours,  etc. 
Buckwheat,  1  bag,  3|  Ib. 
Corn  meal,  1  bag,  3|  Ib. 
Graham,  1  bag,  3^  Ib. 
Macaroni,  1  box,  12  oz.  . 
Rye,  1  bag,  3|  Ib.       .     . 
Spaghetti,  12  oz.  box 
Wheat,  1  bag,  3^  Ib   .      . 
Wheat,  1  bag,  7  Ib.    .      . 
Wheat,  1  bag,  24£  Ib       . 
Whole  wheat,  1  bag,  5  Ib. 

WEED    CHEMISTRY  18 


276  CHEMISTRY   IN   THE   HOME 

FOODS  PRIMARILY  OF  PLANT  ORIGIN  —  Continued 


FOOD  AS  WE  BUY  IT 

NOURISHMENT  IN  THIS  FOOD 

*§g 

2«?£ 

aS  x  5 

§s§& 

feglS 

OD       W  H 

£3*w 

H  g  B 
P 

Muscle 
Builder 

For  Heat  and  Energy 

Protein 

Fat 

Carbohy- 
drates 

(Starch 
and  Sugar) 

Fruit 
Apples,  1  qt.,  28  oz.    .     . 
Bananas,  1  doz.,  4^  Ib.    . 
Cherries,  1  can,  30  oz.     . 
Cranberries,  1  Ib.    .     .     . 
Dates,  1  box,  12  oz.    .     . 
Figs   1  Ib       

Pounds 
.01 
.04 
.02 
.01 
.01 
.04 
.01 
.03 
.04 
.01 
.01 
.01 
.02 

.01 
.00 

.12 
.09 
.08 
.06 
.20 
.07 
.05 
.07 

.00 
.01 
.00 

Pounds 
.01 
.02 
.00 
.01 
.02 
.00 
.01 
.02 
.01 
.00 
.01 
.01 
.00 

.00 
1.00 

.30 
.34 
.31 
.26 
.29 
.12 
.33 
.27 

.00 
.00 
.00 

Pounds 
.19 
.64 
.40 
.10 
.53 
.74 
.14 
.26 
.60 
.19 
.31 
.64 
.73 

.50 
.00 

.10 
.04 
.06 
.04 
.19 
.04 
.06 
.07 

.02 
.04 
.19 

Calories 
385 
1350 
778 
215 
1088 
1475 
335 
615 
1200 
385 
621 
1251 
1400 

950 

4226 

1660 
1655 
1575 
1265 
1935 
706 
1620 
1375 

61 
96 
370 

Grapes,  1  Ib  
Lemons,  1  doz.,  3  Ib. 
Oranges,  1  doz.,  5|  Ib.     . 
Peaches,  1  can,  28  oz. 
Pears,  1  can,  28  oz.     .     . 
Pineapple,  1  can,  28  oz.  . 
Prunes,  1  Ib  

Jellies  (average  analysis) 
1  jar   10  oz.  .               .     . 

Miscellaneous 
Olive  oil,  1  pt.  bottle,  1  Ib. 

Nuts 
Almonds,  1  Ib.        ... 
Brazil  nuts,  1  Ib.         . 
Filberts   1  Ib 

Hickory  nuts,  1  Ib.      .     . 
Peanuts  1  Ib 

Peanut  butter,  1  jar,  \  Ib. 
Pecans,  1  Ib  
Walnuts,  1  Ib  

Pickles 
Cucumber,  14|  oz.  bottle. 
Mixed,  1  bottle,  14  oz.     . 
Spiced,  1  bottle,  14  oz.    . 

FOODS 


277 


FOODS  PRIMARILY  OF  PLANT  ORIGIN  —  Continued 


NOURISHMENT  IN  THIS  FOOD 

?Jg* 

,  Muscle 
'Builder 

For  Heat  and  Energy 

O  £  OL) 

FOOD  AS  WE  BUY  IT 

O  H  K 

pt|   O   W   EH 

Carbohy- 

r\  y*i-f  rf-kt* 

ffiaWH 

Protein 

Fat 

(J.I  cttcb 

(Starch 

Hg  5 

and  Sugar) 

Pies 

Pounds 

Pounds 

Pounds 

Calories 

Apple,  1,  2|  Ib.       .     .     . 

.07 

.22 

.96 

2857 

Custard,  1,  2|  Ib.   .     .     . 

.09 

.14 

.58 

1867 

Mince,  1,  21  Ib.      ... 

.14 

.28 

.86 

3003 

Soup 

Asparagus,   cream   of,    1 

can,  1  Ib  

.03 

.03 

.05 

285 

Bouillon,  1  can,  1  Ib. 

.02 

.00 

.00 

50 

Celery,  cream  of,  1  can, 

1  Ib        

.02 

.03 

.05 

235 

Chicken,  1  can,  1  Ib. 

.04 

.00 

.02 

100 

Consomme,  1  can,   1  Ib. 

.03 

.00 

.00 

55 

Corn,  cream  of,  1  can,  1  Ib. 

.03 

.02 

.08 

270 

Mock  turtle,  1  can,  1  Ib. 

.05 

.01 

.03 

185 

Mulligatawny,  1  can,  1  Ib. 

.04 

.00 

.06 

180 

Oxtail,  1  can,  1  Ib.      .     . 

.04 

.01 

.04 

170 

Pea,  1  can,  1  Ib. 

.04 

.01 

.08 

235 

Pea,  cream  of,  1  can,  1  Ib. 

.03 

.03 

.06 

270 

Tomato, 

.02 

.01 

.06 

185 

Turtle,  1  can,  1  Ib.      . 

.06 

.02 

.04 

265 

Vegetable,  1  can,  1  Ib.     . 

.03 

.00 

.01 

65 

Sugars  and  Starches 

Candy,  1  Ib  

.00 

.00 

.96 

1680 

Cornstarch,    1    package, 

1  Ib 

.00 

.00 

.90 

1675 

Sugar,  brown,  1  Ib.     .     . 

.00 

.00 

.95 

1765 

Sugar,  gran.,  1  bag,  3^  Ib. 

.00 

.00 

3.50 

6510 

Sugar,  maple,  1  Ib.      .     . 

.00 

.00 

.82 

1540 

Sugar,  powdered,  1  Ib.     . 

.00 

.00 

1. 

1860 

Molasses,  1  can,  29  oz.   . 

.04 

.00 

1.25 

2338 

Tapioca,  1  package,  14  oz. 

.00 

.00 

.77 

210 

278 


CHEMISTRY   IN   THE   HOME 


FOODS  PRIMARILY  OF  PLANT  ORIGIN  —  Continued 


(H 

NOURISHMENT  IN  THIS  FOOD 

5|g. 

i 
JVluscle 

o      •<  £ 

Builder 

For  Heat  and  Energy 

ogop 

FOOD  AS  WE  BUY  IT 

O  ^  K 

Carbohy- 

^ °|  w 

Protein 

Fat 

drates 
(Starch 

H  H  5 

andSugar) 

H 

Vegetables 

Pounds 

Pounds 

Pounds 

Calories 

Asparagus,  1  can,  28  oz. 

.02 

.00 

.05 

149 

Beans,  string,  1  qt.     .     . 

.04 

.01 

.12 

315 

Beets,  1  bunch,  2  Ib.  .     . 

.02 

.00 

.15 

340 

Cabbage,  1  head,  4  Ib.     . 

.01 

.00 

.17 

500 

Carrots,  1  bunch,  10  oz. 

.01 

.00 

.05 

100 

Cauliflower,  1  head,  2  Ib. 

.04 

.01 

.09 

280 

Celery,  1  bunch,  10  oz.    . 

.00 

.00 

.01 

44 

Corn,  1  can,  19  oz. 

.03 

.01 

.23 

540 

Cucumber,  1  large,  12  oz. 

.01 

.00 

.02 

51 

Eggplant,  1  Ib.        ... 

.01 

.00 

.05 

130 

Lettuce,  1  head,  10  oz.    . 

.01 

.00 

.02 

51 

Mushrooms,  1  Ib.        .     . 

.04 

.00 

.07 

210 

Onions,  1  qt.,  28  oz.    .     . 

.03 

.01 

.16 

359 

Parsnips,  1  bunch,  24  oz. 

.02 

.01 

.16 

360 

Peas,  canned,  1  can,  20  oz. 

.04 

.01 

.17 

419 

Peas,  green,  1  qt.,  28  oz. 

.06 

.00 

.17 

446 

Potatoes,  Irish,  1  basket, 

6  Ib 

.10              H1 

.88 

1860 

Potatoes,  sweet,  1  qt.,  28 

oz  

.02 

.01 

.38 

805 

Radishes,  1  bunch,  5  oz. 

.00 

.00 

.01 

30 

Spinach,  1  qt.,  28  oz. 

.04 

.01 

.06 

193 

Succotash,  1  can,  19  oz.  . 

.04 

.01 

.22 

540 

Tomatoes,  1  Ib.      ... 

.01 

.00 

.04 

105 

Tomatoes,  canned,  1  can, 

38  oz.     .     . 

.03 

.01 

.10 

249 

Turnips,  1,  3  Ib.     .     .     . 

.03 

.00 

.17 

375 

FOODS  279 

FOODS  PRIMARILY  OF  ANIMAL  ORIGIN 


FOOD  AS  WE  BUY  IT 

NOURISHMENT  IN  THIS  FOOD 

(H 

Q 

fc  0  0 

d«?£ 
§gg| 

£g^h 

2QW  s 

£»* 

P 

Muscle 
Builder 

For  Heat  and  Energy 

Protein 

Fat 

Carbohy- 
drates 
(Starch 
and  Sugar) 

Beef 
Chuck,  roast  or  steak,  1 
Ib 

Pounds 

.15 
.14 
.26 
.19 
.20 

.19 

.17 
.17 
.14 
.12 

.00 
.05 
.21 
.26 
.01 
.06 
.06 

.08 
.01 

.20 

.08 
.10 
.01 

Pounds 

.00 
22 
]07 
.20 
.03 

.09 

.17 
.12 
.07 
.01 

.85 
.06 
.01 
.34 

.08 

.18 
.08 

.07 

.83 

.14 

.01 
.01 
.06 

Pounds 

.00 
.00 
.00 
.00 
.03 

.00 

.00 
.00 
.00 
.00 

.00 
.01 
.04 
.02 
.02 
.44 
.10 

.48 
.00 

.00 

.00 
.00 
.00 

Calories 

920 
1195 
780 
1185 
555 

745 

985 
825 
545 
270 

3605 
330 
510 
1950 
430 
1808 
650 

1323 
3525 

935 

200 
201 
460 

Corned,  1  Ib  

Dried,  1  Ib  
Flank,  roast  or  steak,  1  Ib. 
Liver,  1  Ib  
Round,  roast  or  steak,  1 
Ib 

Sirloin,  roast  or  steak,  1  • 
Ib  
Sweetbreads,  1  Ib.       .     . 
Tongue,  1  Ib  

Tripe,  1  Ib  

Dairy  Products 
Butter,  1  Ib  
Buttermilk,    1   qt.,   2  Ib. 
Cheese,  cottage,  1  Ib. 
Cheese,  American,    1   Ib. 
Cream,  1  bottle,  |  pt.,  8oz. 
Ice  cream,  1  qt.,  2  Ib. 
Milk,  1  qt.,  2  Ib.     .     .     . 
Milk,  condensed,   1  can, 
14|  oz. 

Oleomargarine,  1  Ib.   . 

Eggs 
Hens',  1  doz.,  1|  Ib.    .     . 

Fish 
Bass,  1  Ib  

Blue,  1  Ib      . 

Butter,  1  Ib.  .     .     . 

280  CHEMISTRY  IN  THE   HOME 

FOODS  PRIMARILY  OF  ANIMAL  ORIGIN — Continued 


FOOD  AS  WE  BUY  IT 

NOURISHMENT  IN  THIS  FOOD 

THIS  FOOD  CAN 
YIELD  TO  THE  BODY 
IN  ENERGY  AND 
HEAT  UNITS 

M  uscle 
Builder 

For  Heat  and  Energy 

Protein 

Fat 

Carbohy- 
drates 
(Starch 
and  Sugar) 

Fish  (con't) 
Cod,  fresh,  1  Ib.      ... 
Cod,  salt,  1  Ib.        ... 
Flounder,  1  Ib.        ... 
Halibut,  steak,  1  Ib.    .     . 
Halibut,  smoked,  1  Ib. 
Mackerel,  1  Ib.       ... 
Salmon,  1  can,  12  oz. 
Shad   1  Ib 

Pounds 
.18 
.22 
.06 
.15 
.21 
.14 
.18 
.09 
.09 

.13 
.14 
.13 
.16 

.14 
.15 

.17 
.14 

.13 
.13 
.15 
.00 

.18 
.19 
.20 

Pounds 
.08 
.27 
.00 
.04 
.15 
.06 
.07 
.05 
.05 

.01 
.12 
.30 

.18 

.28 
.15 

.03 
.23 

.36 
.26 
.33 
1. 

.20 
.24 
.19 

Pounds 
.00 
.00 
.00 
.00 
.00 
.00 
.00 
.00 
.00 

.00 
.00 
.00 
.00 

.00 
.00 

.00 
.00 

.00 
.00 
.00 
.00 

.00 
.00 
.01 

Calories 
165 
1020 
130 
470 
1020 
525 
638 
380 
380 

295 

775 
1500 
1475 

1445 
900 

440 
1235 

1740 
1340 
1670 
4226 

1170 
1380 
1170 

Trout,  lake,  1  Ib.    .     .     . 

Poultry  and  Game 
Chickens,  broilers,  1  Ib. 
Fowl  1  Ib      . 

Goose,  1  Ib  
Turkey   1  Ib 

Lamb 
Chops,  1  Ib  
Leg,  1  Ib  

Mutton 
Kidnev,  1  Ib  

Leg,  1  Ib 

Pork 
Bacon,  1  Ib  
Chops,  loin,  1  Ib.    .     .     . 
Ham,  1  Ib  

Lard,  1  Ib. 

Sausages 
Bologna,  1  Ib. 

City,  beef  and  pork,  1  Ib. 
Frankfurters,  1  Ib.       .     . 

FOODS 


FOODS  PRIMARILY  OF  ANIMAL  ORIGIN  —  Continued 


281 


NOURISHMENT  IN  THIS  FOOD 

s|s. 

Muscle 
Builder 

For  Heat  and  Energy 

gggS 

FOOD  AS  WE  BUY  IT 

O  ^  P3 

Carbohy- 

^ °  1  ^ 

Protein 

Fat 

drates 
(Starch 

«Sg« 

and  Sugar) 

(H 

Shell  fish 

Pounds 

Pounds 

Pounds 

Calories 

Clams,  1  doz.,  5  Ib.     .     . 

.10 

.00 

.05 

350 

Lobsters,  1,  heavy,  3  Ib. 

.16 

.02 

.00 

400 

Oysters,  1  qt.,  2  Ib.     .     . 

.12 

.02 

.06 

460 

Scallops,  1  qt.,  2  Ib.    .     . 

.30 

.00 

.07 

690 

Veal 

Breast,  1  Ib  

.15 

.09 

.00 

645 

Cutlets   1  Ib 

20 

08 

00 

690 

Leg,  1  Ib  

.18 

.06 

.00 

585 

Liver   1  Ib 

.19 

.02 

.00 

575 

SUMMARY 

Our  foods  must  be  both  inorganic  and  organic.  Water  and  mineral 
matter  comprise  the  inorganic  foods.  Carbohydrates,  fats 
and  oils,  and  protein,  the  organic  foods. 

Protein  builds  up  the  tissues  and  is  the  only  food  that  can  do  this. 

Carbohydrates  and  fats  (including  oils)  furnish  heat  and  energy  to 
the  body. 

A  balanced  ration  is  necessary  to  health. 

Food  requirement.  Under  ordinary  conditions  a  man  requires 
•fa  of  an  ounce  of  protein  for  each  pound  he  weighs  and  enough 
fats  and  carbohydrates  to  furnish  2500-3000  Calories  daily. 

Exercises 

1.  Name  two  animal  and  two  vegetable  foods  rich  in  (a)  protein, 
(6)  fat  or  oils,  (c)  carbohydrates. 

2.  How  should  a  farmer 's  dietary  differ  from  that  of  a  book- 
keeper's?   Why? 


282  CHEMISTRY   IN   THE   HOME 

3.  From  what  foods  do  we  obtain  the  mineral  matter  needed 
for  our  bodies  ? 

4.  Compute   the   protein   you   consumed   yesterday,    and   the 
Calories  your  food  provided.     Was  your  diet  well  balanced  ?     How 
could  it  have  been  improved? 

5.  Make  out  suitable  meals  for  a  day  for  yourself.     (Use  the 
one-portion  food  table.) 

6.  How  does  a  vegetarian  obtain  the  protein  necessary  for  his 
body? 

7.  How  would  the  number  of  articles  of  food  in  a  meat  and 
vegetable  diet  compare  with  the  number  in  a  diet  that  was  purely 
vegetable  ? 

8.  By  the  use  of  the  family  food  table  determine  whether  your 
family  is  being  well  and  economically  nourished. 


CHAPTER   XXIV 
FOOD    PRESERVATION 

Importance  of  food  preservation.  In  hundreds  of  ways 
science  is  making  our  lives  easier,  and  one  of  these  ways  is 
in  teaching  us  how  to  preserve  foods  so  that  we  may  enjoy 
meats,  fruits,  and  vegetables,  at  all  times,  instead  of  only  in 
their  season. 

The  table  of  a  laborer  is  to-day  provided  the  year  around 
with  foods  that  two  hundred  years  ago  not  even  a  king  could 
have  obtained,  and  for  this  we  must  thank  science,  which 
has  taught  us  how  to  preserve  foods  from  decay.  To  under- 
stand how  to  prevent  the  decay  of  foods  we  must  first  under- 
stand the  causes  of  their  decay. 

The  fungi.  The  green  coloring  matter  of  plants,  called 
chlorophyll,  with  the  aid  of  the  energy  of  sunlight,  is  able 
to  convert  the  carbon  dioxide  of  the  air  into  the  complex 
compounds  found  in  plants. 

One  great  group  of  plants,  the  fungi,  contains  no  chloro- 
phyll, and  this  lack  renders  them  unable  to  prepare  their 
food  from  carbon  dioxide.  They  must  start  from  organic 
matter  that  has  been  elaborated  by  other  plants  or  animals ; 
that  is,  they  are  saprophytes.  Our  common  fungi,  the  mush- 
rooms and  toadstools,  are  examples  of  such  plants.  It  is 
to  these  fungi  that  the  decay  and  spoiling  of  foods  is  almost 
entirely  due. 

There  are  three  great  divisions  of  these  colorless  plants 
that  we  must  consider,  —  the  molds,  the  yeasts,  and  the  bac- 

283 


284 


CHEMISTRY    IN    THE    HOME 


teria.    To  call  these  colorless  plants  is  likely  to  lead  to  a 
misunderstanding.     They  may  be  highly  colored   in  reds, 
browns,  or  grays,  but  not  greens,  for  the  absence  of  the  green 
coloring  matter,  chlorophyll,  is  characteristic  of  the  group. 
Molds  and  their  spores.     Molds  are  large  enough  to  be 
seen  by  the  naked  eye.    There  are  many  varieties,  but  as 
their  methods  of  growth  and  reproduction  are  similar,  we 
need  not  distinguish  between  them.     If  you  will  expose  moist 
g  o  j »  0  pieces  of   bread,  potato, 

banana,  or  cheese,  to  the 
air,  and  allow  them  to 
stand  undisturbed  in  a 
warm  place  for  a  few 
days,  you  will  have 
abundant  opportunity  to 
study  mold  growth  (Fig. 
99). 

You   will   notice   that 
first   white    threads,  the 

mycelium,  grow  down  into  the  host  of  the  mold.  These 
rapidly  increase  in  size  and  number,  and  throw  out 
branches  until  the  bread  is  filled  with  them.  After  two  or 
three  days,  the  surface  of  the  mold  becomes  colored.  This 
color  may  be  a  brown,  red,  or  blue,  depending  on  the 
variety  of  the  mold.  This  color  shows  that  the  mold  is 
fruiting,  or  producing  reproductive  bodies  called  spores. 

Close  examination  of  the  common  blue  mold,  even  with- 
out the  aid  of  a  lens,  will  show  that  the  mold  has  thrown  up 
above  its  surface  tiny  stalks,  each  bearing  at  the  top  a  colored 
ball.  Examination  under  the  microscope  shows  that  these 
balls  contain  hundreds  of  small  bodies  called  spores.  As 
the  mold  matures,  these  balls  break  open,  and  the  spores 


FIG.  99.  —  Mold,  producing  spores. 


FOOD   PRESERVATION  285 

escape  to  be  borne  away  by  the  winds,  and  to  cause  more 
trouble  to  the  housewife. 

How  to  avoid  molds.  The  conditions  necessary  for  the 
germination  of  the  mold  spores  are  moisture,  warmth,  and 
food.  This  gives  us  the  clew  to  the  means  of  avoiding  molds. 
Jellies  are  usually  covered  with  a  paper  or  with  paraffin. 
When  a  spore  drops  on  this  covering,  it  can  obtain  no  food, 
and  so  does  no  harm.  If,  however,  a  spore  has  fallen  on 
the  jelly  before  the  cover  is  put  on,  it  will  germinate.  Soon 
the  top  of  the  jelly  will  be  covered  with  a  thick  coating  of 
mold,  and  the  upper  part  of  the  contents  spoiled. 

Most  molds  are  not  harmful,  so  that  the  contents  of  the 
jar  need  not  be  thrown  away.  If  the  mold  itself,  and  the 
soft  jelly  immediately  under  it,  are  removed,  the  remainder 
is  fit  for  use.  If,  after  the  jelly  has  been  poured  into  the 
glasses,  and  has  hardened,  the  surface  is  brushed  over  with 
brandy,  the  alcohol  will  kill  any  spores  present.  It  may  now 
be  covered  with  the  assurance  that  it  will  not  mold.  Cover- 
ing foods  helps  to  keep  them. 

Common  molds  grow  best  at  a  temperature  of  from  70° 
to  100°  F.  Keeping  food  in  the  refrigerator  will  then  help 
to  prevent  the  growth  of  molds.  A  few  varieties,  however, 
grow  best  at  a  temperature  of  40°  F.,  and  these  will  of 
course  grow  freely  in  an  ordinary  ice  chest. 

A  temperature  of  150°  F.  will  kill  any  mold  that  has  started 
to  germinate.  Some  spores  will  resist  this  temperature. 
To  make  sure,  therefore,  that  canned  fruit  will  not  mold, 
it  should  be  heated  to  150°  F.  Allow  it  to  stand  for  a  day. 
During  this  time  any  spores  present  will  start  to  grow. 
Heating  a  second  time  will  kill  these,  and  the  fruit  will  keep 
with  certainty. 

The  presence  of  moisture  aids  the  growth  of  mold  upon 


286  CHEMISTRY    IN    THE    HOME 

almost  any  organic  material.  Leather  is  safe  as  long  as  it 
is  dry,  but,  allowed  to  become  moist,  it  will  mildew,  and  mil- 
dew is  one  of  the  forms  of  mold.  Dry  food,  as  crackers,  is 
never  troubled  with  these  annoying  visitors.  The  drying 
of  foods  is  an  important  method  of  preserving  foods. 

The  housewife  should  prevent  any  molds  that  may  grow 
in  the  kitchen  from  fruiting  and  scattering  spores  to  make 
other  foods  mold.  Foods  should  be  kept  cool,  and  where 
possible  in  the  light,  as  most  molds  grow  best  in  the  shade. 

Most  important  of  all,  foods  should  be  kept  dry.  The 
importance  of  this  is  well  seen  in  apples.  Every  grocer  will 
tell  you  that  cold  storage  apples  do  not  keep  long  after 
removal  from  the  cold  storage  warehouse.  This  is  largely 
because,  when  they  are  removed  from  the  cold  rooms,  they 
condense  a  film  of  water  on  their  skins.  Any  spores  that 
fall  on  them  will  then  stick  fast.  The  moisture  remains 
longest  where  the  apples  touch  each  other,  and  therefore 
the  apples  start  to  decay  there.  If,  after  the  apples  have 
warmed  to  the  temperature  of  his  store,  the  grocer  would 
carefully  wipe  each  one,  the  tendency  to  spoil  would  be 
greatly  lessened. 

Wrapping  fruit  in  paper  tends  to  preserve  it,  for  not  only 
does  the  paper  keep  spores  from  falling  on  the  fruit,  but,  be- 
ing absorbent,  keeps  the  surface  of  the  fruit  dry.  Knowing 
the  life  history  of  the  molds,  you  can  see  why  one  rotten  apple 
will  infect  a  whole  barrel.  As  the  mold  matures,  the  spores 
scatter,  and  soon  all  of  the  fruit  is  covered  with  them.  Every 
break  in  the  skin  is  then  an  invitation  for  spores  to  enter 
and  grow,  and  they  quickly  accept  the  opportunity  offered. 

Flavors  due  to  molds.  Sometimes  molds  are  purposely 
introduced  into  food  to  give  it  a  characteristic  flavor.  Roque- 
fort cheese  when  first  made  is  entirely  lacking  in  its  well- 


FOOD   PRESERVATION 


287 


known  taste.  To  produce  this,  wires  are  first  thrust  into 
ripe  cheese.  They  are  then  thrust  into  the  new  cheese.  In 
this  way  the  mold  from  the  ripe  cheese  is  introduced  into 
the  new  cheese,  where  it  grows  and  produces  the  green  color 
and  pleasant  flavor.  Brie,  Stilton,  and  Camembert  are 
other  cheeses  the  flavors  of  which  are  at  least  partly  due  to 
molds.  All  of  these  cheeses  should  be  eaten  when  just  ripe, 
as  the  continued  growth  of  the  molds  finally  makes  the 
flavor  too  strong  to  be  agreeable. 

Yeasts  and  how  they  grow.  Yeasts  are  microscopic  oval 
plants  that  reproduce  by  a  process  called  budding.  Exam- 
ining yeast  under  the  micro- 
scope, you  can  see  little  more 
than  oval  colorless  bodies, 
about  ^oir o  °f  an  inch  in  diame- 
ter (Fig.  100).  If  you  continue 
your  watch,  you  will  see  a  small 
knob  form  on  one  end  of  the 
yeast  plant.  The  cell  wall 
draws  in,  dividing  this  knob 
from  the  original  plant,  the 
two  break  apart,  and  we  have 
two  plants.  In  this  way  yeast 
plants  increase  in  numbers  with 
great  rapidity. 

The  enzyme  of  yeast.  The  yeast  plant  secretes  a  sub- 
stance known  as  zymase.  This  is  one  of  a  class  of  bodies 
known  as  enzymes  (also  called  ferments] . 

When  studying  oxygen,  we  found  that  the  decomposition 
of  potassium  chlorate  took  place  at  a  lower  temperature 
if  we  added  manganese  dioxide,  yet  after  the  oxygen  was 
all  given  off,  the  manganese  dioxide  remained  unchanged. 


FIG.  100.  —  Yeast  plant. 


288  CHEMISTRY    IN    THE    HOME 

The  enzymes  are  compounds  that  serve  a  similar  purpose, 
and  we  may  call  them  by  the  same  name,  catalytic  agents. 
Their  presence  enormously  increases  the  speed  of  certain 
chemical  changes. 

There  are  many  of  these  enzymes  or  digestive  ferments 
in  the  body.  Ptyalin  is  found  in  the  saliva,  and  changes 
starch  to  sugar.  Pepsin  is  found  in  the  gastric  juice,  and 
changes  proteins  to  peptones  and  proteoses.  Trypsin  is 
found  in  the  pancreatic  juice,  and  has  much  the  same  action 
as  pepsin.  The  particular  action  that  is  aided  by  zymase 
is  the  change  of  sugars  into  carbon  dioxide  and  alcohol. 

C6H12O6  ->  2  C2H5OH  +  2  CO2 

Yeast  in  bread  making.  The  use  of  yeast  in  making 
bread  light  has  been  known  from  antiquity.  Leavened 
bread  was  bread  made  light  by  adding  leaven  to  the  dough. 
This  leaven  was  dough  saved  from  a  previous  baking,  and 
contained  yeast. 

Yeast  spores  are  found  floating  in  the  air  everywhere, 
and  if  dough  is  exposed  to  the  air,  some  of  these  "  wild 
yeasts  "  are  sure  to  fall  into  it.  These  wild  yeasts  are  not 
always  desirable  additions,  for  some  of  them  cause  the  bread 
to  taste  sour. 

From  these  wild  yeasts  the  cultivated  yeast  of  to-day  has 
been  obtained.  The  yeast  plants  are  placed  in  large  vats, 
mashed  potato  and  hops  added,  and  the  whole  kept  at  a  tem- 
perature of  80°  F.  Yeast  plants  multiply  rapidly,  the  con- 
tents of  the  vat  becoming  thick  and  frothy.  The  yeast 
is  then  thrown  on  a  cheesecloth,  to  remove  some  of  the 
excess  water.  When  well  drained,  starch  is  mixed  with  it 
to  make  it  firmer,  and  it  is  cut  into  cakes  and  sold  as  com- 
pressed yeast. 


FOOD   PRESERVATION  289 

If  yeast  is  gently  dried,  it  passes  into  a  dormant  state, 
in  which  state  it  is  sold  as  dry  yeast  cakes.  These  are  used 
where  a  supply  of  yeast  must  be  kept  for  some  time,  as  com- 
pressed yeast  will  not  keep  long. 

The  carbon  dioxide  produced  by  the  action  of  yeast  in 
dough  makes  the  bread  porous,  and  more  easily  digested, 
owing  to  the  larger  surface  exposed  to  the  action  of  the 
digestive  juice.  Biscuits  raised  with  baking  powder,  and 
aerated  bread,  contain  the  same  ingredients  as  ordinary 
bread,  but  have  a  very  different  flavor. 

Fermented  drinks.  All  fermented  drinks,  from  home- 
made root  beer  to  champagne,  are  made  by  the  action  of 
yeast  on  sugar.  In  root  beer  a  small  quantity  of  a  highly 
flavored  extract  is  mixed  with  sugar,  yeast,  and  water,  and 
bottled.  Fermentation  occurs,  and  the  carbon  dioxide 
produced  makes  the  liquid  bubble  and  froth  when  the  bottle 
is  opened. 

It  must  be  remembered  in  using  these  homemade  bever- 
ages, that  alcohol  is  produced  in  addition  to  the  carbon 
dioxide,  and  that,  if  the  fermentation  continues  for  several 
days,  an  amount  of  alcohol  is  produced  as  great  as  that 
contained  in  a  light  beer. 

Kumiss  is  made  by  adding  yeast  and  sugar  to  milk. 
The  mixture  is  allowed  to  ferment  for  a  day,  and  then 
bottled.  When  cool  it  is  ready  for  use.  It  is  claimed 
that  it  is  more  digestible  than  raw  milk,  and  is  used  by 
invalids. 

Manufacture  of  grain  alcohol.  Ethyl  alcohol,  or  grain 
alcohol,  C2H5OH,  is  made  by  converting  the  starch  of  grain 
into  sugar,  fermenting  this,  and  distilling  the  alcohol.  Grain, 
as  barley,  is  spread  out  on  floors  to  a  depth  of  six  inches. 
It  is  kept  moist  and  warm.  The  grain  starts  to  germinate, 


290  CHEMISTRY    IN    THE    HOME 

when  the  diastase  present  changes  the  starch  of  the  grain 
to  sugar. 

As  soon  as  the  maximum  amount  of  sugar  has  been  ob- 
tained, the  grain  is  ground,  and  yeast  and  water  added. 
Fermentation  takes  place,  and  alcohol  is  produced.  The 
mixture  is  distilled,  and  as  alcohol  boils  at  a  lower  tempera- 
ture than  water,  the  distillate  contains  all  of  the  alcohol, 
mixed  with  a  good  deal  of  water.  The  dilute  alcohol  is 
then  again  distilled  to  concentrate  it.  In  this  way  the  95% 
alcohol  of  the  druggist  is  prepared. 

Properties  of  alcohol.  Alcohol  is  a  colorless,  volatile 
liquid,  lighter  than  water,  and  miscible  with  it.  It  burns 
with  a  very  hot,  almost  colorless,  blue  flame.  It  is  the 
intoxicating  constituent  of  all  fermented  drinks.  It  is 
widely  used  as  a  fuel,  and  as  a  solvent.  Resins  and  oils 
dissolve  in  it  freely.  Shellac  varnish  is  a  solution  of  shellac 
in  alcohol.  The  tinctures  of  the  druggist,  as  tincture  of 
iodine,  are  all  solutions  in  alcohol. 

Denatured  alcohol.  The  government  levies  a  heavy  tax 
on  alcohol  that  can  be  used  for  drinking  purposes.  Formerly 
this  tax  was  a  burden  on  the  manufacturer  of  chemicals, 
who  uses  large  quantities  of  alcohol  as  a  solvent.  To  meet 
industrial  needs,  the  government  allows  what  is  called  de- 
natured alcohol  to  be  sold  tax  free.  This  is  alcohol  to  which 
some  substance  has  been  added  that  renders  it  unfit  for 
drinking,  but  does  not  interfere  with  its  use  as  a  fuel  or 
solvent.  Denatured  alcohol  can  be  sold  at  about  one  fifth 
the  price  of  pure  alcohol,  as  it  pays  no  tax. 

Wood  alcohol.  When  wood  is  distilled,  one  of  the 
products  obtained  is  wood  alcohol,  or  methyl  alcohol, 
CH3OH.  This  is  a  light,  colorless  liquid,  having  a  dis- 
agreeable odor.  It  is  used,  like  grain  alcohol,  as  a  fuel 


FOOD   PRESERVATION 


291 


and  a  solvent.  It  is  a  poison,  and  must  not  be  used  in 
beverages. 

Ether.  By  distilling  a  mixture  of  strong  sulphuric  acid 
and  alcohol,  ether  is  obtained. 

2  C2H5OH  +  H2S04  -^  (C2H5)20  +  H2SO4  +  H2O 

Ether  is  a  very  volatile,  colorless  liquid,  having  a  character- 
istic odor.  Its  vapor  is  very  heavy  and  inflammable.  Ether 
is  used  by  surgeons  as  an  anaesthetic. 

Manufacture  of  vinegar.  When  sweet  cider  is  exposed 
to  the  air,  it  first  turns  hard ;  that  is,  yeast  converts  the  sugar 
into  alcohol.  If  this  hard  cider  is  allowed  to  stand,  it 
is  converted  into  cider  vine- 
gar. This  is  due  to  the 
action  of  mother-of-vinegar. 
An  examination  of  mother- 
of-vinegar  under  the  micro- 
scope shows  that  it  is  com- 
posed of  myriads  of  bacteria. 
Vinegar,  then,  which  is  a 
weak  solution  of  acetic  acid, 
is  one  of  the  products  of  bac- 
terial action,  and  we  should 
expect  that  any  dilute  solu- 
tion of  alcohol  would  be  acted 
upon  in  the  same  way. 

Much  of  the  vinegar  used  in  pickling  is  prepared  from 
alcohol.  It  is  the  ordinary  "  malt  vinegar  "  or  "  white 
wine  vinegar  "  of  trade.  A  large  cylinder  is  filled  with 
wood  shavings,  placed  on  trays  so  that  they  cannot  pack 
too  closely  together.  These  shavings  are  first  soaked  in 
vinegar,  to  impregnate  them  with  mother-of-vinegar.  Pro- 

WEED    CHEMISTRY 19 


FIG.  101.  — Bacteria  in  mother-of- 
vinegar. 


292 


CHEMISTRY    IN    THE    HOME 


vision  must  be  made  by  means  of  holes  for  the  passage  of 
air  through  the  cylinder,  for  the  change  of  alcohol  to  acetic 

acid  is  really  an  oxidation  of  the 
alcohol  (Fig.  102). 

Dilute  alcohol  is  then  allowed  to 
trickle  slowly  through  the  cylinder. 
As  it  passes  over  the  shavings, 
which  are  covered  with  the  neces- 
sary bacteria,  the  alcohol  is  con- 
verted into  acetic  acid.  If  the 
conversion  is  not  complete  by  one 
passage  through,  the  liquid  that 
runs  from  the  bottom  of  the  cylin- 
der is  returned  to  the  top  and  run 
through  again. 

The  product  is  satisfactory  for 
cooking  and  pickling  processes,  but 
lacks  the  flavor  of  cider  vinegar. 
It  has  sometimes  been  a  tempta- 
tion that  the  manufacturer  could  not  resist  to  add  a  little 
caramel  to  the  product.  This  gives  it  the  color  of  cider 
vinegar,  and  it  is  sold  under  that  name. 

Bacteria  and  how  they  reproduce.  Bacteria  are  still 
smaller  than  either  molds  or  yeasts.  They  are  so  small 
indeed  that  the  highest  powers  of  the  microscope  are  needed 
to  see  them,  and  even  these  high  powers  do  little  more  than 
show  us  moving  dots.  One  of  the  largest  of  these  bacteria 
is  about  ioljo  "o  °^  an  mc^  l°ng>  while  many  are  not  more 
than  sTfirnr  °f  an  mcn  m  diameter. 

It  is  only  within  the  past  few  decades  that  we  have  known 
anything  about  these  minute  forms  of  life,  for  they  are 
invisible  to  the  eye,  and  their  study  even  under  the  micro- 


FIG.   102.  —  Vinegar  making. 
Quick  process. 


FOOD   PRESERVATION  293 

scope  tells  us  little  about  them.  They  are  very  simple  in 
structure,  and  it  is  quite  impossible  in  many  cases  to  identify 
the  variety  by  looking  at  them.  We  must  test  them  to  see 


FIG.  103.  —  Bacteria.      (1),  Typhoid  fever.      (2-5),  F,orms  of  bacteria  found 

in  milk. 

what  they  can  do.  In  form,  they  are  usually  spherical, 
rod-shaped,  or  spiral. 

Bacteria  multiply  by  simple  division.  A  rod-shaped 
individual  will  lengthen,  and  then  divide  in  two.  This 
process  is  named  fission.  Reproduction  is  very  rapid,  some 
bacteria  dividing  every  half  hour.  This  accounts  for  their 
immense  numbers,  for  if  every  individual  divides  every  half 
hour,  at  the  end  of  six  hours  there  would  be  4096,  and  at 
the  end  of  24  hours  about  17,000,000  bacteria  all  descended 
from  one  parent. 

These  organisms  are  plants,  but  have  the  power  to  move. 
In  popular  usage  bacteria  are  called  germs,  and  all  kinds  of 
malign  influences  are  attributed  to  them.  This  idea  is  not 
quite  right.  It  is  true  that  certain  varieties,  called  the 
pathogenic  bacteria,  cause  certain  diseases.  Thus,  consump- 
tion, typhoid  fever,  and  diphtheria  are  caused  by  the  presence 
in  the  body  of  certain  bacteria.  The  pathogenic  bacteria 
are,  however,  in  a  small  minority,  the  nonpathogenic  forms 
far  outnumbering  them. 

These  nonpathogenic  forms  are  of  great  importance  to 
us.  They  destroy  the  organic  refuse  of  the  world,  and  return 
its  elements  to  the  soil  in  such  a  form  that  plants  can  use 


294  CHEMISTRY    IN    THE    HOME 

them.  They  are  of  great  importance  to  the  farmer.  One 
form  in  particular  fixes  the  nitrogen  of  the  air,  that  is,  changes 
the  free  nitrogen  of  the  air  which  plants  cannot  assimilate 
into  a  nitrate  which  they  can  use. 

These  nitrifying  bacteria  are  often  found  associated  with 
the  legumes,  such  as  peas,  beans,  lentils,  clover,  and  alfalfa. 
They  grow  in  nodules  on  the  roots  of  these  plants  and  make 
the  soil  fertile.  In  starting  a  new  field  of  alfalfa,  the  ground 
should  always  be  inoculated  with  these  nitrifying  bacteria 
before  planting  the  alfalfa  seed.  This  is  done  by  sprinkling 
dirt  from  an  old  alfalfa  field  over  the  ground  of  the  new 
field.  Bacteria  are  also  useful  to  the  dairyman,  for  the 
flavor  of  butter  and  cheese  depends  on  their  action,  as  well 
as  on  that  of  the  molds. 

Some  pathogenic  bacteria  cause  diseases  to  which  only 
certain  forms  of  animal  life  are  subject.  Advantage  is 
sometimes  taken  of  this  to  exterminate  rats  and  mice. 
Food  is  spread  around  that  contains  these  bacteria.  The 
mice  and  rats  eat  it,  and  die  of  the  disease  that  it  produces. 
Other  animals  can  eat  the  food  with  impunity,  as  they  are 
not  subject  to  the  disease  caused  by  these  bacteria. 

How  to  control  bacteria.  To  the  housewife,  however, 
bacteria  are  always  a  trouble,  for  it  is  their  presence  and 
activity  that  make  the  preservation  of  food  difficult.  We 
must  then  study  the  conditions  that  favor  their  growth, 
so  that  we  may  know  how  to  control  them.  Most  of  the 
common  forms  grow  best  at  the  ordinary  temperature,  or  a 
temperature  slightly  higher.  A  few,  however,  grow  best  at 
a  temperature  only  slightly  above  freezing.  Keeping  food 
cold  will  then  help  to  preserve  it. 

Certain  kinds  of  bacteria  multiply  by  spores.  These 
are  formed  inside  of  the  individual  bacteria,  break  through 


FOOD   PRESERVATION  295 

the  cell  wall,  and  float  around  until  they  find  a  suitable  grow- 
ing place.  These  forms  are  very  difficult  to  get  rid  of,  for 
their  spores  are  so  resistant  that  even  boiling  them  for  a 
short  time  will  not  kill  them. 

Boiling  will  kill  practically  all  bacteria.  Their  spores,  how- 
ever, will  resist  boiling  for  a  short  time,  so  that  to  be  sure 
that  food  is  sterile,  that  is,  contains  no  bacteria,  we  must 
either  boil  it  for  an  hour,  or  boil  it  for  a  short  time,  allow  it 
to  cool  and  stand,  so  that  any  spores  present  will  develop, 
and  then  boil  again.  Merely  warming  the  food  will  not 
answer,  for  this  only  causes  the  bacteria  to  grow  the  faster. 

Light  is  a  great  enemy  of  bacteria.  They  grow  best  in 
dark,  damp,  dirty  corners.  To  keep  our  houses  as  free  as 
possible  from  these  enemies,  we  must  have  plenty  of  sun- 
light streaming  into  every  room.  The  sunlight  may  fade 
the  carpet,  but  this  is  of  no  consequence,  compared  to  the 
preservation  of  our  health.  Light  is  especially  fatal  to  the 
pathogenic  forms.  In  sickrooms,  then,  the  common  practice 
of  keeping  the  room  dark  is  not  to  be  recommended.  A  light 
room  will  not  only  make  the  patient  more  cheerful,  but  will 
assist  in  controlling  the  disease  by  killing  the  germs  that 
may  caus?  it  in  others. 

Like  molds,  bacteria  require  water  for  their  growth. 
There  is  this  difference,  however :  molds  grow  best  on  acid 
foods,  while  bacteria  grow  best  on  slightly  alkaline  materials. 
Fruits  therefore  decay  by  the  action  of  molds,  while  meats 
spoil  by  the  action  of  bacteria.  This  rule  is  not  of  universal 
application,  but  is  generally  true. 

Where  bacteria  are  found.  Bacteria  are  found  every- 
where. An  examination  of  the  saliva,  of  the  dust  of  a  room, 
or  of  a  bank  note,  will  show  their  presence  in  large  numbers. 
Small  as  they  are,  they  are  somewhat  heavier  than  the  air, 


296  CHEMISTRY    IN    THE    HOME 

and  therefore  settle  to  the  floor,  where  they  can  easily  be 
found  in  quantities. 

In  cleaning  a  room  the  common  practice  of  sweeping,  and 
then  dusting  with  a  feather  duster,  simply  stirs  up  the 
bacteria,  and  they  find  new  and  less  desirable  growing  places. 
It  is  better  to  use  an  oiled  cloth  and  wipe  the  dust  away. 

Many  diseases  are  spread  by  a  disregard  of  these  facts. 
The  saliva  of  a  consumptive  contains  the  bacteria  that 
cause  the  disease.  If,  then,  the  consumptive  spits  in  the 
street,  and  the  saliva  dries,  many  of  these  bacteria  will  be 
set  free  to  float  in  the  air,  to  be  drawn  into  the  lungs  of 
healthy  persons,  and  so  expose  them  to  the  danger  of  infec- 
tion. Too  great  care  cannot  be  exercised  in  keeping  these 
pathogenic  forms  under  control. 

Action  of  bacteria  on  proteins.  Proteins  form  the  main 
food  of  bacteria.  Their  action  causes  its  putrefaction  and 
makes  the  food  unfit  for  use.  Even  food  that  shows  no 
outward  sign  of  their  action  may  be  dangerous,  for,  in  addi- 
tion to  the  products  arising  from  the  decay  of  the  food  itself, 
bacteria  secrete  some  poisonous  compounds.  These  are 
called  ptomaines.  Fish,  shellfish,  and  ice  cream  are  very 
likely  to  develop  ptomaines,  especially  in  the  summer. 
They  often  cause  severe  and  sometimes  fatal  poisoning. 

Pasteurization  of  milk.  Different  varieties  of  bacteria 
produce  different  results.  Thus,  the  mother-of-vinegar 
bacteria  change  alcohol  to  acetic  acid.  One  other  variety 
is  troublesome  to  the  housewife,  the  variety  that  changes 
milk  sugar  to  lactic  acid,  and  thus  causes  milk  to  sour. 
This  variety  does  not  form  spores,  and  is  killed  by  exposure 
to  a  temperature  of  155°  F. 

To  keep  milk  sweet,  then,  it  should  be  heated  to  155°  F. 
This  process  is  called  pasteurization.  Milk  heated  to  this 


FOOD   PRESERVATION 


297 


temperature  does  not  have  the  taste  of  boiled  milk,  nor  are 
the  albuminoids  coagulated,  as  they  are  in  boiled  milk. 
To  pasteurize  milk  it  should  be  placed  in  bottles,  and  these 
placed  in  a  double  boiler 
and  heated  to  from  155°- 
170°  for  twenty  minutes 
(Fig.  104).  The  milk 
should  then  be  cooled  rap- 
idly, and  kept  cold.  If 
pasteurized  milk  is  kept 
at  ordinary  temperatures, 
it  will  spoil  more  quickly 
than  raw  milk.  Although 
pasteurized  milk  does  not 
sour,  it  is  subject  to  putre- 
faction and  should  not  be 
kept  over  24  hours. 

Preservation  by  cooling 
and  drying.  One  of  the 
best  means  of  preserving  food  is  to  keep  it  cold.  The  use  of 
refrigerators,  and  of  cold  storage,  is  universal  for  this  pur- 
pose. Even  cold  storage  will  not,  however,  keep  food  in- 
definitely, and  a  limit  should  be  placed  on  the  length  of  time 
food  may  remain  in  cold  storage.  As  you  learned  in  the 
previous  paragraphs,  cold  storage  is  efficacious  because  most 
molds  and  bacteria  do  not  grow  in  the  cold. 

Keeping  food  dry  also  tends  to  preserve  it.  Dried  fruits, 
fish,  and  meats  are  all  examples  of  the  use  of  this  method 
of  preserving  food.  Its  usefulness  is  due  to  the  fact  that 
bacteria  and  molds  require  moisture  for  their  growth. 

Preservation  by  canning.  Boiling  will  preserve  foods, 
for  this  kills  the  bacteria,  and  if  the  food  is  protected  from 


FIG.  104.  —  Pasteurizing  apparatus. 


298  CHEMISTRY    IN    THE    HOME 

fresh  infection,  it  will  keep  a  long  time.  The  canned  vege- 
tables that  form  such  a  large  proportion  of  the  stock  of  the 
grocer  are  examples  of  this  method  of  preservation. 

The  vegetables  are  washed,  cut  up  if  necessary,  and  placed 
in  tin  cans.  The  cans  are  then  covered  and  heated,  often 
under  pressure  to  raise  the  boiling  temperature,  until  the 
vegetable  is  cooked.  The  cans  are  then  sealed.  The  diffi- 
culty in  the  process  comes  in  being  sure  that  every  form  of 
microorganism  is  killed  by  the  heating.  If  a  single  spore 
survives,  the  contents  of  the  can  will  spoil,  and,  as  some  of 
the  bacteria  spores  are  very  resistant,  it  is  difficult  to 
be  sure  that  they  are  all  killed.  Properly  canned  foods 
keep  indefinitely,  and  the  process  has  been  a  boon  to 
humanity. 

The  canning  of  fruit  at  home  depends  on  the  same  prin- 
ciples. If  the  fruit  jars,  the  rubbers,  and  the  tops  are 
sterile,  and  the  fruit  is  heated  until  it  too  is  sterile,  the  fruit 
will  keep.  If,  however,  the  rings  are  washed  in  cold  water, 
or  the  hot  fruit  allowed  to  stand  open  in  the  jars  for  a  while, 
it  will  probably  not  keep.  Can  you  now  explain  why  pre- 
serves sometimes  "  work,"  and  why,  when  they  are  opened, 
bubbles  of  gas  are  seen  and  the  preserves  have  an  alcoholic 
smell? 

Chemical  preservatives.  Foods  are  sometimes  kept  by 
the  use  of  chemical  preservatives.  These  must  have  two 
properties.  They  must  have  antiseptic  powers,  and  they 
must  be  harmless  to  man.  There  are  many  substances  such 
as  mercuric  chloride,  corrosive  sublimate,  that  will  prevent 
the  growth  of  the  microorganisms  that  cause  food  to  spoil. 
Corrosive  sublimate  is,  however,  a  violent  poison,  and  so 
cannot  be  used.  Other  substances  as  sugar,  salt,  spices, 
vinegar,  and  the  smoke  from  smoldering  wood,  have  a  pre- 


FOOD   PRESERVATION  299 

servative  action,  and  are  regarded  as  harmless.  Still 
another  class  of  preservatives,  including  borax,  boracic 
acid,  benzoic  acid  and  benzoates,  salicylic  acid  and  sali- 
cylates,  and  sulphites,  is  used. 

Some  of  these,  used  in  small  quantities,  are  probably 
harmless.  Their  use,  however,  makes  it  possible  for  the 
manufacturer  to  use  material  that  is  unfit  for  human  con- 
sumption. If  tomato  catsup  can  be  made  without  the  use 
of  any  preservative,  why  should  we  buy  a  product  that 
contains  a  preservative?  It  may  be  harmless,  and  the 
material  used  by  the  maker  may  be  of  a  high  grade,  but  so 
long  as  its  use  makes  it  possible  to  use  inferior  materials, 
and  so  long  as  it  is  not  certain  that  preservatives  are  harm- 
less, why  buy  the  doubtful  products? 

There  is  another  objection  to  their  use.  Even  the  manu- 
facturers who  use  these  preservatives  claim  only  that  they 
are  harmless  in  small  quantities.  Now  if,  as  sometimes 
happens,  much  of  the  food  served  at  a  meal  is  canned,  and 
if  each  of  the  articles  contains  only  a  little  preservative, 
the  total  amount  that  we  consume  may  be  considerable. 
It  is  therefore  a  wise  rule  to  avoid  their  use  altogether. 
Never  buy  food  preserved  with  sodium  benzoate  or  other  pre- 
servatives, even  if  their  use  is  allowed  by  law. 

One  notable  example  of  the  use  of  such  harmful  preserva- 
tives is  the  use  of  formaldehyde  in  milk.  This  will  preserve 
the  milk,  that  is,  the  milk  will  not  turn  sour,  but  it  will 
rot.  Its  use  is  illegal,  but  some  cheap  milks  contain  it. 
If  milk  will  not  sour  in  the  ordinary  length  of  time,  you  may 
be  sure  that  a  preservative  has  been  added.  Never  buy 
or  use  such  milk. 

The  same  thing  is  true  of  all  foods.  Whenever  you  find 
a  brand  of  catsup  that  will  not  spoil,  or  sausages  that  do 


300  CHEMISTRY    IN    THE   HOME 

not  go  bad,  do  not  use  them.  They  must  contain  preserva- 
tives, and  it  is  best  to  avoid  all  such  food  products. 

Antiseptics.  The  same  agents  used  in  the  preservation 
of  foods  may  also  be  used  as  disinfectants,  and  here  we 
must  be  sure  that  we  understand  the  meaning  of  certain 
terms.  A  deodorizer  is  a  substance  that  destroys  a  noxious 
odor  or  covers  it  up  with  a  stronger  one.  Many  deodorizers 
are  of  no  value,  indeed  are  harmful,  for  their  use  leads  to 
the  belief  that  the  cause  of  the  odor  has  been  removed, 
which  is  not  the  case.  A  liberal  use  of  cologne  may  cover 
up  the  odor  of  perspiration,  but  it  will  not  obviate  the 
necessity  for  bathing. 

An  antiseptic  is  a  material  that  checks  the  growth  of 
bacteria.  It  may  not,  however,  kill*  all  of  those  present. 
A  germicide  is  a  material  that  kills  all  bacteria.  Antiseptics, 
when  used  in  quantities,  are  generally  germicides. 

To  disinfect  is  to  remove  the  cause  of  trouble.  If  chlorine 
oxidizes  decaying  matter,  it  is  a  disinfectant.  If  corrosive 
sublimate  is  used  in  a  strength  that  will  kill  all  bacteria 
and  prevent  putrefaction,  it  is  a  disinfectant.  We  have 
already  seen  that  both  heat  and  sunlight  will  kill  bacteria. 
We  may  use  both  of  these  as  disinfectants. 

The  number  of  chemical  disinfectants  is  great,  but  there 
are  five  that  can  so  easily  be  used  at  home  that  you  ought 
to  know  something  of  them.  One  of  the  most  important 
is  mercuric  chloride,  called  corrosive  sublimate,  HgCl2. 
Used  at  the  strength  of  1  to  1000  of  water,  it  is  quickly 
fatal  to  all  microorganisms.  It  is  intensely  poisonous, 
and  this  limits  its  use  to  places  where  there  is  no  danger 
of  its  being  swallowed. 

Bleaching  powder,  or  chloride  of  lime,  is  extensively  used. 
Its  value  depends  upon  the  liberation  of  chlorine.  When 


FOOD   PRESERVATION  301 

the  damp  material  ceases  to  have  a  strong  odor,  it  is  ex- 
hausted, and  should  be  replaced  by  fresh. 

Carbolic  acid,  or  phenol,  is  an  excellent  disinfectant. 
It  is  not  as  efficient  as  either  corrosive  sublimate  or  chloride 
of  lime,  but  is  used  more  than  either.  It  is  an  intense 
poison,  and  must  be  handled  with  care. 

Formaldehyde.  Formaldehyde,  or  formalin,  is  one  of 
the  best  disinfectants  for  home  use.  Formaldehyde"  is  a 
gas  with  a  disagreeable  odor.  It  is  soluble  in  water,  and  a 
40%  solution  of  it  is  sold  as  formalin.  It  has  no  effect  on 
fabrics,  and  so  clothes  that  need  to  be  disinfected  may  be 
soaked  in  it. 

One  of  the  difficulties  of  effectively  disinfecting  a  room 
is  to  make  sure  that  all  parts  of  the  room  come  into  contact 
with  the  disinfectant.  Formaldehyde  is  a  gas,  and,  if  it  is 
liberated  in  a  room  in  quantity,  every  part  of  the  room 
will  be  disinfected. 

Formaldehyde  polymerizes,  that  is,  several  molecules 
combine  together  to  form  a  new  molecule.  This  polymer 
is  called  paraformaldehyde.  It  is  a  white  solid,  which  on 
heating  changes  back  into  the  gas  formaldehyde.  The 
solid  is  heated  over  a  lamp  and  is  thus  made  to  give  off  the 
disinfecting  gas.  This  is  an  easy  and  efficacious  way  of 
disinfecting  a  room. 

Sulphur  dioxide.  Sulphur,  when  burned,  forms  the  gas 
sulphur  dioxide,  SO2.  This  gas  is  easily  oxidized,  forming 
sulphur  trioxide,  SO3.  It  is  therefore  a  good  reducing  agent. 
For  this  reason  it  is  used  as  a  bleaching  agent,  especially  for 
straw,  and  dried  fruits.  A  mass  of  sulphur,  burned  in  a 
closed  room,  is  a  fair  disinfectant,  but  not  so  good  as  for- 
maldehyde. It  has  the  advantage  that  sulphur  can  be 
bought  anywhere,  and  its  use  requires  no  especial  apparatus. 


302  CHEMISTRY    IN    THE    HOME 

The  gas  sulphur  dioxide  is  easily  compressed  to  a  liquid 
and  is  sold  in  the  liquid  state  in  tin  cans  having  an  opening 
closed  by  a  lead  pipe.  To  use  these  cans  to  disinfect  a 
room,  it  is  only  necessary  to  close  the  room  as  tightly  as 
possible,  sealing  all  cracks  by  pasting  paper  over  them, 
then  cut  the  lead  pipe.  This  allows  the  sulphur  dioxide 
to  flow  out.  Place  the  can  on  a  tin  dish,  go  out,  and  close 
the  door.  The  liquid  changes  to  a  gas,  which,  going  every- 
where in  the  room,  disinfects  it. 

SUMMARY 

Molds  cause  foods  to  spoil.     They  propagate  by  spores.     They 

require  moisture,  warmth,  and  food,  before  they  can  grow. 

Heat  kills  them.     Certain  foods,  as  cheese,  owe  their  flavor 

to  them. 
Yeast  contains  zymase,  which  changes  sugar  to  alcohol  and  carbon 

dioxide. 
An  enzyme  is  an  organic  catalytic  agent  which  hastens  certain 

specific  chemical  changes. 
Ethyl  alcohol,  or  grain  alcohol,  is  prepared  by  the  action  of  yeast 

on  sugar.     The  product  is  distilled  to  purify  it.     It  is  used 

in  beverages,  as  a  fuel,  and  as  a  solvent. 
Denatured  alcohol  is  alcohol  made  nonpotable  by  the  addition  of 

wood  alcohol,  etc. 
Ether  is  ethyl  oxide.     It  is  made  by  taking  one  molecule  of  water 

from  two  molecules  of  alcohol.     It  is  used  as  an  anaesthetic. 
Vinegar  is  made  by  the  action  of  mother-of-vinegar  on  alcohol. 

It  is  dilute  acetic  acid. 
Bacteria    are    microorganisms.      They    multiply    with    enormous 

rapidity  by  fission.     They  cause  foods,   especially  protein, 

to  putrefy,  and  are  useful  as  they  destroy  organic  waste. 
Pathogenic  bacteria  cause  disease.     Boiling  kills  them. 
Ptomaines  are  poisonous  bodies  produced  by  certain  bacteria. 
Pasteurization  is  heating  milk  to  155°  F.     This  kills  the  bacteria 

that  produce  lactic  acid  and  sour  the  milk. 


FOOD   PRESERVATION  303 

Keeping  food  dry  and  cold  preserves  it,  because  this  prevents  the 
growth  of  bacteria  and  molds. 

Harmless  preservatives  :*  sugar,  salt,  spices,  vinegar,  and  the  smoke 
from  smoldering  wood  will  preserve  food.  These  preservatives 
are  harmless. 

Chemical  preservatives  to  be  avoided :  borax  and  boracic  acid, 
benzoates  and  benzoic  acid,  salicylates  and  salicylic  acid,  and 
sulphites,  will  preserve  foods.  They  are  all  probably  some- 
what harmful.  Formaldehyde  is  a  poison  and  should  never 
be  used  as  a  food  preservative. 

A  deodorizer  covers  up  a  bad  odor  with  a  stronger  one.  It  is 
of  no  value. 

An  antiseptic  is  a  material  that  checks  the  growth  of  bacteria. 

A  germicide  is  a  material  that  kills  all  bacteria. 

Household  disinfectants:  mercuric  chloride,  chloride  of  lime, 
carbolic  acid,  formaldehyde,  and  sulphur  dioxide. 

Exercises 

1.  Why  is  it  important  to  prevent  molds  from  forming  spores? 

2.  Why  do  preserves  sometimes  "work"? 

3.  Why  do  not  preserves  in  strong  sirup  spoil,  even  if  left  open? 

4.  Why  do  canned  soups  sometimes  spoil? 

5.  What  would  you  conclude  if  bottled  milk  kept  sweet  for 
four  days? 

6.  Why  does  sweet  cider  become  hard? 

7.  Name  two  enzymes  and  explain  what  each  does. 

8.  If  vinegar  is  only  dilute  acetic  acid,  why  not  use  dilute  sul- 
phuric acid  instead?     It  would  be  cheaper. 

9.  How  can  druggists  keep  "  fresh  fruit  "  for  soda  fountain 
use  on  their  counters  for  days  without  its  spoiling? 


CHAPTER  XXV 
SILICON,    SILICA,    AND    SILICATES 

Silicon.  It  is  remarkable  that  the  second  most  abundant 
element  is  not  known,  even  by  name,  to  the  majority  of 
people.  Silicon  constitutes  28%  of  the  earth's  crust,  and 
yet  you  probably  never  saw  even  one  specimen  of  the  pure 
element.  This  is  because  it  always  exists  naturally  in  com- 
pounds, either  as  the  dioxide,  or  as  a  silicate.  It  resembles 
carbon  in  its  chemical  properties. 

It  is  reduced  from  its  compounds  with  great  difficulty. 
But  with  the  aid  of  the  electric  furnace  it  is  now  made  in 
large  quantities.  The  element  is  a  brown,  crystalline  body, 
which  burns  readily  in  the  air.  The  element  itself  is  of 
no  importance  in  the  home,  but  its  compounds  are  in  use  by 
every  one. 

Silica  and  its  varieties.  Silicon  dioxide,  SiO2,  known  also 
as  silica,  occurs  distributed  everywhere  in  nature.  In  the 
form  of  quartz  it  constitutes  the  bulk  of  sand,  and  of  many 
soils.  Many  plants  contain  it;  the  coating  of  rattan,  for 
example,  is  almost  pure  silica. 

When  pure,  it  crystallizes  in  six-sided  prisms,  topped 
by  six-sided  pyramids  (Fig.  105).  These  clear,  colorless 
crystals  are  called  rock  crystals  and,  when  cut,  are  rhine- 
stones.  Many  of  the  stones  sold  under  such  names  as 
"  Congo  diamonds  "  are  cut  from  quartz. 

Quartz  is  harder  than  glass,  and  has  only  a  small  coefficient 
of  expansion.  That  is,  it  expands  very  little  on  heating.  A 
dish  made  of  quartz  can  therefore  be  heated  red-hot  and  then 

304 


SILICON,   SILICA,   AND   SILICATES 


305 


plunged  into  ice  water  without  breaking.     This,  together 
with  the  fact  that  quartz  is  infusible  at  a  white  heat  and 


FIG.    105.  —  Quartz  crystals. 

is  unaffected  by  most  chemical  reagents,  makes  it  valuable 
in  the  laboratory  for  dishes  and  crucibles.  These  were 
formerly  so  expensive  that  chemists  could  not  afford  to  use 
them,  but  they  are  now  made  cheaply  by  the  use  of  the 
electric  furnace. 

The  colors  in  quartz  are  due  to  small  amounts  of  im- 
purities. A  little  manganese  colors  it  violet,  and  makes  the 
semiprecious  stone,  the  amethyst.  Other  impurities  pro- 
duce smoky  quartz,  or  the  cairngorm  stone  of  Scotland, 
rose  quartz,  chalcedony,  jasper,  carnelian,  and  the  so-called 
yellow  topaz. 

Opal  is  quartz  containing  some  water.  Its  play  of  color 
is  due  to  fine  cracks  in  the  stone,  which  cause  an  interference 
of  light.  These  colors  are  produced  in  the  same  way  as  are 
the  colors  in  a  soap  bubble. 


306  CHEMISTRY   IN   THE   HOME 

Many  of  these  stones  when  cut  are  of  a  beautiful  color. 
They  all  have,  however,  the  disadvantage  of  being  soft, 
compared  to  the  precious  stones,  and  so  do  not  hold  their 
polish  when  subjected  to  hard  wear. 

Sand  is  broken-up  quartz,  and,  when  cemented  together, 
makes  sandstone.  Flint,  too,  is  a  variety  of  quartz.  Quartz 
sand  is  used  in  making  glass,  porcelain,  and  as  a  building 
material  in  mixing  mortar  and  cement. 

Silica  as  an  abrasive.  Quartz  is  largely  used  as  an  abrasive 
and  polishing  material.  Sandpaper  consists  of  sharp  sand 
glued  to  paper.  The  shells  of  certain  small  water  plants, 
the  diatoms,  are  largely  silica.  When  they  die,  their  soft 
parts  decay,  but  the  shell  being  silica  remains,  falls  through 
the  water,  and  forms  a  layer  of  mud  on  the  bottom  of  the 
water.  The  shell  remains  of  these  diatoms  are  called  dia- 

tomaceous  earth,  or  infusorial 
earth  (Fig.  106).  When  freed 
from  impurities,  it  is  sold  as  a 
polishing  powder. 

Examine  some ' 'electro-silicon" 
under  the  microscope,  and  you 
will  see  the  curious  structure  of 
the  silica  valves  of  these  diatoms. 
Agate.  Quartz  is  insoluble  in 
pure  water,  but  in  the  presence  of 

FIG.   106.  —  Diatoms.      (X  50.) 

an  alkali  it  will  slowly  dissolve. 

Since  many  natural  waters,  especially  in  the  western  part  of 
our  country,  are  alkaline,  quartz  dissolves  in  them.  This  dis- 
solved quartz  may  be  precipitated  by  an  acid.  It  is  in  this 
way  that  agates  are  formed.  Water  containing  silica  runs 
into  a  hole  in  the  rock,  the  quartz  is  deposited,  and  forms  a 
layer.  Sometimes  the  water  is  clear  and  leaves  a  clear  layer. 


SILICON,    SILICA,    AND    SILICATES 


307 


Sometimes  it  is  muddy  and  leaves  a  brown  or  black  ring. 
In  this  way  the  banded  structure  of  the  agate  is  produced. 
The  brilliantly  colored  agates  are  all  colored  artificially. 

Common  silicates.  Silicon  forms  a  large  number  of  acids 
known  as  silicic  acids.  Their  salts,  called  silicates,  make  up 
the  bulk  of  the  rocks  of  the  earth.  Feldspar,  slate,  soap- 
stone,  serpentine,  asbestos,  and  talc  are  all  silicates.  We 
may  easily  prepare  sodium  silicate  in  the  laboratory,  by 
fusing  together  sand  and  sodium  carbonate,  and  dissolving 
the  resulting  mass.  Sodium  silicate  is  called  water  glass,  or 
soluble  glass,  and  is  used  as  a  cement  for  asbestos  and  glass, 
in  preserving  eggs,  and  by  calico  printers  and  soap  makers. 

Making  glass.  Among  the  artificial  silicates  the  most 
important  is  glass.  By  melting  together  in  a  large  clay  pot, 
sand,  calcium  car- 
bonate (marble),  and 
sodium  sulphate  or 
carbonate,  a  trans- 
parent viscous  mix- 
ture of  sodium  and 
calcium  silicates 
obtained.  This 
glass. 

If  the  materials 
used  are  perfectly 
pure,  a  colorless 
glass  results.  The 
presence  of  iron  as 
an  impurity  gives  us 
green  bottle  glass.  By  purposely  adding  a  coloring  agent, 
we  can  produce  glass  of  any  color.  Cobalt  gives  a  blue, 
manganese,  a  violet,  and  chromium,  a  green  color  to  glass. 

WEED    CHEMISTRY 20 


IS 


IS 


FIG.  107.  —  Glass  furnace.  The  glass  is 
melted  in  clay  pots  (A  A)  which  are  sur- 
rounded by  hot  gases. 


308 


CHEMISTRY   IN  THE  HOME 


Many  glass  utensils  are  blown.  The  workman  pushes 
the  end  of  an  iron  tube  (the  blowpipe)  into  the  mass  of 
molten  glass,  and  collects  a  ball  of  the  thick  material  on 

the  end  of  his  blow- 
pipe. By  blowing 
through  the  blow- 
pipe, this  ball  is 
changed  into  a  bub- 
ble of  glass,  and,  as 
it  is  soft,  the  work- 
man can  form  it 
into  any  required 
shape,  as  a  bottle 
or  tumbler. 

Window  glass  is 
made  by  blowing  a 
large  bubble  and 
then  swinging  it 
until  it  stretches 
out  into  a  cylinder 
(Fig.  108).  The 
top  and  bottom  of 
this  cylinder  are 
then  cut  off,  and  the 
cylinder  cracked 
down  one  side.  It  is  then  placed  on  a  hot  iron  plate,  the 
cracked  side  uppermost.  The  heat  softens  the  glass,  and 
the  cylinder  slowly  opens,  forming  a  sheet.  This  is  flat- 
tened as  much  as  possible  by  pressing  it  against  the  iron 
plate  with  an  iron  instrument  resembling  a  spade.  Nat- 
urally the  sheet  of  glass  is  never  quite  flat,  hence  the 
unevenness  of  our  window  glass. 


(6)     Reheating. 
FIG.  108.  — Window  glass  making. 


SILICON,    SILICA,   AND   SILICATES 


309 


Plate  glass.  If  we  wish  perfectly  flat  glass,  we  must  use 
plate  glass.  This  is  made  by  pouring  molten  glass  upon  an 
iron  table  having  a  ledge  all  around  it  to  keep  the  glass  from 
running  off.  A  heavy  roller  is  then  passed  over  it  to  flatten 
it.  This  gives  a  thick  sheet  of  glass.  It  is  then  ground  and 
polished  on  both  sides.  As  much  of  the  glass  is  wasted  in 


(a)    Getting  a  lump  of  glass  on  the  blowpipe.  (b)    Blowing  a  bottle  in  a  mold. 

FIG.   109.  —  Bottle  making. 

the  grinding  and  polishing,  and  as  the  cost  of  these  two 
operations  is  high,  plate  glass  is  much  more  costly  than 
ordinary  glass. 

Molding  glass  bottles.  Many  bottles  are  molded,  instead 
of  being  blown  into  shape.  The  blowpipe,  having  a  lump 
of  glass  on  its  end,  is  inserted  into  a  mold.  The  workman 
blows  through  the  pipe,  thus  forcing  the  glass  to  take  the 
shape  of  the  mold  (Fig.  109).  The  mold  is  then  opened,  and 
the  completed  bottle  taken  out.  Usually  a  ridge  left  by  the 
place  where  the  mold  opens  can  be  seen  on  such  bottles. 


310  CHEMISTRY   IN   THE   HOME 

Any  variation  in  the  amount  of  glass  used  will  alter  the 
thickness  of  the  walls  of  the  bottle,  and  this  will  alter  its 
capacity.  To  be  sure  that  the  bottle  will  hold  the  required 
amount,  it  is  weighed.  An  automatic  weighing  machine  is 
used  that  will  reject  the  bottle  unless  its  weight  falls  be- 
tween certain  fixed  limits.  In  this  way  the  bottles  that 
are  too  thin  or  too  thick  are  detected  and  remelted. 

Making  glass  tubing.  Glass  tubing  is  made  by  blowing 
a  small  bubble  of  air  into  a  ball  of  glass  on  the  end  of  a  blow- 
pipe. A  blowpipe  is  then  stuck  in  the  side  of  the  glass  ball 
opposite  to  the  first,  and  the  two  workmen  run  in  opposite 
directions.  This  stretches  the  ball  out  into  a  tube.  By 
varying  the  size  of  the  air  bubble  in  the  original  ball  of 
glass,  and  the  speed  at  which  the  men  run,  large  or  small 
tubes,  with  thick  or  thin  walls,  can  be  made. 

Chemical  glass.  Many  glasses  contain  silicates  of  other 
metals  than  sodium  and  calcium.  For  chemical  glassware 
a  potassium  calcium  glass,  called  Bohemian  glass,  is  used, 
as  it  is  harder  and  more  infusible  than  the  sodium  calcium 
glass.  For  the  glass  used  in  photographic  lenses,  the  most 
diverse  mixtures  of  silicates  are  used. 

Cut  glass.  Cut  glass  is  made  from  a  lead  glass,  that  is, 
glass  containing  lead  silicate.  It  is  heavy,  and  takes  a 
beautiful  luster  on  being  polished.  To  make  a  cut  glass 
bowl,  the  heavy  bowl  shape  is  first  molded.  The  design 
is  then  drawn  on  this  with  chalk  and  then  cut  on  sandstone 
wheels.  This  leaves  the  glass  rough  and  like  ground  glass. 
It  is  then  polished,  using  rouge  or  some  similar  polishing 
powder.  It  is  this  cutting  and  polishing  that  make  cut  glass 
expensive. 

Ground  glass.  Ground  glass  is  made  by  the  use  of  a  sand 
blast.  Sand  is  blown  by  compressed  air  against  the  surface 


SILICON,    SILICA,   AND    SILICATES  311 

of  ordinary  window  glass.  Each  grain  of  sand  as  it  strikes 
the  glass  makes  a  tiny  scratch,  and  these  scratches  crossing 
and  recrossing  each  other  make  the  glass  translucent.  Fine 
ground  glass  is  also  made  by  pouring  dilute  hydrofluoric  acid 
on  a  glass  plate. 

Graduating  glassware.  Glass  resists  the.  action  of  most 
chemicals,  but  hydrofluoric  acid,  HF,  dissolves  it.  Advan- 
tage is  taken  of  this  in  marking  thermometers  and  graduates. 
The  stem  of  the  thermometer  is  first  covered  with  wax.  This 
is  scratched  through  with  a  needle  where  the  graduations  are 
to  come,  and  hydrofluoric  acid  poured  on.  This  dissolves 
the  glass  wherever  it  has  been  exposed,  and  has  no  action 
on  the  wax.  In  this  way  lines  or  letters  are  placed  on  glass. 

Formation  of  clay.  So  many  minerals  are  silicates  that  a 
mere  list  of  their  names  would  fill  several  pages  of  this  book. 
Meerschaum  is  a  silicate  of  magnesium;  garnet  and  horn- 
blende are  both  silicates  of  calcium  and  magnesium ;  mica  is 
a  silicate  of  potassium  and  aluminium ;  feldspar  is  a  silicate 
of  aluminium  and  sodium  or  potassium ;  and  asbestos  is  a 
silicate  of  magnesium.  These  are  only  a  few  examples  of 
the  many  important  common  silicates. 

The  familiar  rock,  granite,  used  in  building  and  for  monu- 
ments, is  composed  of  a  mixture  of  quartz,  feldspar,  and 
usually  mica  or  hornblende.  Long-continued  action  of 
air  and  water  eventually  breaks  up  the  granite.  Quartz 
is  set  free  as  sand ;  mica,  being  light,  is  washed  away ;  and 
feldspar  remains.  This  feldspar  disintegrates,  the  sodium 
or  potassium  silicates  wash  out,  and  aluminium  silicate  is 
left.  This  is  called  clay.  When  free  from  all  impurities, 
it  is  a  white,  earthy  mass,  called  kaolin,  Al2Si2O7  •  2  H2O. 

Brick,  tile,  and  stoneware.  Clay  when  heated  becomes 
a  hard  mass.  Bricks  and  tile  are  made  from  it  by  this  pro- 


312 


CHEMISTRY   IN   THE  HOME 


cess.  When  clay  is  mixed  with  water,  it  becomes  plastic. 
This  plastic  clay  is  molded  into  the  shape  of  the  brick  and 
set  aside  to  dry.  When  dry  it  is  "  fired,"  that  is,  heated 
to  a  red  heat  in  a  kiln.  Since  the  clay  used  contains  fusible 
impurities,  these  melt,  and  bind  the  mass  together  into  a 
hard  brick.  If  iron  is  present  in  the  clay,  as  is  usually  the 
case,  the  brick  turns  red.  If  the  clay  is  pure,  a  white  brick 
results. 

Stoneware  and  flower  pots  are  made  by  the  same  method 
as  brick.     To  glaze  them  salt  is  thrown  into  the  kiln  while 

the  stoneware  is  be- 
ing fired.  This  vola- 
tilizes, and  attacks 
the  surface  of  the 
pot,  forming  a  fusible 
sodium  silicate.  This 
melts  and  spreads 
over  the  surface  of 


the  ware,  thus  form- 
ing a  smooth,  im- 
pervious layer  called 
a  glaze.  Such  stone- 
ware as  this  is  cheap, 
but  the  glaze  is  often 
imperfect,  and  the 
ware  itself  is  porous. 
It  is  not  suitable  for  plates,  cups,  saucers,  and  similar  ware. 
Porcelain.  The  best  quality  of  ware  made  from  clay  is 
porcelain.  To  make  this,  pure  clay  is  mixed  with  fine  sand 
and  feldspar,  and  the  whole  is  ground  to  a  fine  powder, 
which  is  mixed  with  enough  water  to  make  a  plastic  mass. 
A  lump  of  this  is  placed  on  a  potter's  wheel,  which  is  a  hori- 


FIG.  110.  —  Inside  a  pottery  kiln. 


SILICON,    SILICA,   AND   SILICATES  313 

zontal  round  board  that  can  be  rotated.  The  potter  rotates 
the  wheel,  and  with  his  fingers  shapes  the  lump  of  clay  into  a 
vase,  plate,  cup,  or  any  other  object  desired.  The  article 
is  then  air  dried  and  fired.  The  feldspar  contained  in  the 
mixture  melts,  and  changes  the  whole  mass  into  translucent, 
white  porcelain. 

The  glaze  used  with  porcelain  is  a  finely  ground  mixture 
of  much  the  same  composition  as  porcelain  itself,  but  more 
fusible.  This  is  mixed  with  water,  and  the  fired  porcelain 
dipped  into  it.  A  thin  coat  of  glaze  is  left  all  over  the  article. 
The  procelain  is  then  fired  again,  the  glaze  melts,  and  forms 
the  smooth  outside  surface  that  we  see  on  our  table  porcelain. 

When  a  considerable  number  of  articles  are  wanted  that 
are  to  be  duplicates,  instead  of  "  throwing  "  the  clay  on  the 
potter's  wheel,  it  is  molded  or  cast.  Plates,  cups,  and 
saucers  are  commonly  made  in  this  way. 

Let  us  suppose  that  we  wish  to  cast  a  cup.  A  plaster  of 
Paris  mold,  having  the  shape  on  the  inside  that  the  cup  is 
to  have,  is  made  in  two  pieces.  The  procelain  mixture  is 
stirred  with  water  until  a  thick  cream  called  slip  is  produced. 
The  halves  of  the  mold  are  then  tied  together  and  the  slip 
poured  in.  The  plaster,  being  porous,  absorbs  water,  and 
a  thin  layer  of  the  porcelain  mixture  sticks  to  the  mold. 
When  this  layer  is  thick  enough,  the  excess  slip  is  poured 
out,  the  halves  of  the  mold  separated,  and  the  cup  taken  out. 
A  piece  of  the  plastic  mixture  is  rolled  out,  and  from  this 
the  handle  of  the  cup  is  formed.  This  is  pressed  on  the  cup 
and  sticks  fast.  It  is  air-dried  and  fired. 

Porcelain  may  be  decorated  by  painting  any  design  on 
its  surface,  using  a  colored  fusible  silicate  as  paint.  When 
the  procelain  is  fired,  this  paint  melts  into  the  glaze,  and 
becomes  a  part  of  it. 


314  CHEMISTRY  IN  THE   HOME 

Cement  and  reenforced  concrete.  Cement  is  made  by 
heating  together  limestone,  clay,  and  sand  in  the  proper 
proportions,  and  grinding  the  resulting  clinker  to  a  dust. 
When  this  is  mixed  with  water,  a  mass  is  produced  that 
becomes  hard,  even  under  water.  Sometimes  a  rock  is 
found  in  nature  containing  all  three  necessary  ingredients 
in  the  proper  proportion.  Such  a  rock  occurs  near  Naples, 
and  was  used  by  the  Romans  to  produce  the  cement  from 
which  they  made  their  famous  aqueducts. 

When  cement  is  mixed  with  sand  and  crushed  stone,  and 
then  water  is  added,  the  mass  hardens  to  an  artificial  stone 
called  concrete.  This  is  extensively  used  for  sidewalks, 
building  foundations,  and  floors.  Concrete  buildings  usually 
contain  iron  rods  imbedded  in  the  concrete.  This  makes 
what  is  known  as  reenforced  concrete.  Such  buildings  are 
almost  everlasting. 

Blast  furnace  slag,  when  mixed  with  limestone,  heated, 
and  ground,  makes  an  excellent  cement.  This  is  another 
good  illustration  of  the  way  that  chemists  are  utilizing 
materials  which  were  formerly  waste  products. 

SUMMARY 

Silicon  is  the  second  most  abundant  element. 

Silicon  dioxide,  silica,  or  quartz  is  a  common  mineral. 

Rock   crystal,    amethyst,   agate,    jasper,   carnelian,    onyx,   are  all 

varieties  of  quartz. 
Sand  is  silica. 

Sandstone  is  sand  cemented  together. 
Opal  is  quartz  containing  water.     Its  fire  is  due  to  cracks  in  the 

stone. 

Sand  paper  is  sharp  sand  glued  on  to  paper. 
Diatomaceous  earth  is  the  silica  valves  of  diatoms.     It  is  used  as 

a  polishing  powder. 


SILICON,   SILICA,   AND   SILICATES  315 

Glass  is  a  mixture  of  silicates.  Window  glass  is  sodium  calcium 
silicate.  Cut  glass  contains  lead  silicate.  Plate  glass  is 
ground  flat  and  then  polished. 

Hydrofluoric  acid  will  attack  glass. 

Pottery  is  made  by  burning  clay. 

Cement  is  clay,  limestone,  and  silica  ground  together  and  heated. 
Mixed  with  sand  and  crushed  stone  it  is  concrete. 

Exercises 

1.  How  could  you  distinguish  stoneware  from  porcelain? 

2.  How  is  cut  glass  distinguished  from  its  imitations? 

3.  What  advantages  has  a  concrete  house? 

4.  Why  are  flower  pots  red,  while  clay  is  white  ? 

5.  How  can  letters  painted  on  glass  bottles  be  made  permanent? 


CHAPTER  XXVI 
TEXTILES 

Fibers  used  in  cloth.  Varied  as  are  the  fabrics  and  weaves 
used  in  dress  goods,  the  fibers  used  to  produce  them  are  few 
in  number.  Silk,  wool,  cotton,  and  linen  are  the  only  four 
of  much  commercial  importance.  Many  others  are  used  in 
small  amounts,  as  hemp,  ramie,  asbestos,  and  jute. 

Characteristics  fibers  should  have.  To  make  it  profitable 
to  spin  fibers,  they  must  possess  a  number  of  characteristics 
which  adapt  them  to  use  in  thread  or  fabric.  Cloth  cannot 
be  woven  until  the  thread  is  spun,  and  to  spin  suitable  thread, 
fibers  having  a  considerable  tensile  strength  are  necessary. 
Fibers  which  are  able  to  resist  a  pull  give  good  wearing 
qualities  to  the  cloth. 

The  fibers,  too,  must  be  long,  as  otherwise  the  thread 
will  not  hold  together.  The  separate  fibers  must  have  some 
ability  to  stick  together,  as  otherwise  the  thread  is  weak. 
They  must  be  pliable,  so  that  they  may  be  easily  bent  in 
weaving.  They  must  be  porous,  or  they  will  not  take  a 
dye,  nor  can  they  be  easily  bleached.  They  must  be  thin, 
as  otherwise  we  cannot  weave  a  fine  cloth.  They  must  be 
of  uniform  size,  as  otherwise  the  cloth  will  not  be  of  uni- 
form thickness.  Lastly,  to  make  weaving  a  commercial 
success  the  fiber  must  be  available  in  large  quantities,  must 
be  cheap,  and  must  wear  well. 

If  you  will  consider  the  above  necessary  qualities  that 
a  fiber  must  have  before  it  is  suitable  for  commercial 

316 


TEXTILES 


317 


FIG.   111.  —  Asbestos;    A,  native  mineral ;   B,  rloth  ;   C,  cord;   D,  strand  of 
fibers  used  in  weaving  cloth. 


318  CHEMISTRY   IN  THE   HOME 

use  on  a  large  scale,  you  will  see  why  only  a  few  of  the 
many  fibers  with  which  nature  provides  us  are  suitable  for 
use. 

Animal  and  vegetable  fibers.  The  common  fibers  may 
be  divided  into  animal  and  vegetable  fibers.  The  animal 
fibers,  wool  and  silk,  are  nitrogenous  compounds.  They 
may  be  distinguished  from  other  fibers  by  the  peculiar  odor 
they  give  when  burning.  Heat  readily  affects  them,  even 
a  moderate  heat  weakening  them  materially.  They  are 
attacked  by  alkalies,  but  withstand  the  action  of  dilute 
acids  better  than  the  vegetable  fibers. 

The  vegetable  fibers,  cotton  and  linen,  are  made  up  of 
plant  cells,  and  are  largely  cellulose.  They  can  withstand 
quite  a  high  temperature  and  the  action  of  alkalies,  but 
acids  attack  them  and  impair  their  strength. 

Asbestos  and  glass  fiber.  Outside  of  these  two  main 
classes,  we  have  such  fibers  as  asbestos.  This  is  a  mineral 
that  occurs  in  long  white  or  greenish  white  fibers.  These 
are  very  fine,  but  possess  little  cohesiveness,  and  are  brittle. 
It  is  therefore  difficult  to  make  a  fine  asbestos  thread.  The 
fibers  can,  however,  be  woven  into  cloth,  and  will  felt  together 
into  a  paperlike  sheet  (Fig.  111). 

Asbestos  is  a  poor  conductor  of  heat,  is  incombustible, 
and  melts  at  a  high  temperature.  The  cloth  woven  from 
it  is  therefore  suitable  for  the  fire  curtain  of  a  theater 
to  shut  off  the  auditorium  from  the  stage  in  case  of  fire, 
for  firemen's  gloves,  for  a  protection  to  woodwork  behind 
stoves,  and  for  similar  uses.  The  mineral  is  cheap,  and 
asbestos  paper,  cloth,  and  sheets  are  used  extensively. 

Glass  can  be  drawn  out  into  fine  thread  and  this  has  been 
used  to  weave  cloth.  Its  commercial  use  is  of  course  im- 
possible, owing  to  its  weight  and  brittleness. 


TEXTILES 


319 


Even  spiders'  web  has  been  used  as  cloth  material,  but 
its  cost  and  scarcity  make  the  product  only  a  curiosity. 

Cotton.  Cotton,  an  impure  form  of  cellulose,  is  the  most 
important  fiber  known.  Our  earliest  records  speak  of  its 
use.  Herodotus  tells  us  of  its  use  in  India,  and  the  army  of 
Xerxes  was  clothed  in  it.  It  is  the  product  of  the  cotton 
plant  that  is  grown  so  largely  in  our  Southern  States.  The 


(a)   Cotton.  (b)    Wool. 

FIG.   112.  —Textile  fibers. 


(c)  Silk. 


world  production  is  enormous,  the  annual  growth  being 
about  18,000,000  bales. 

Under  the  microscope,  it  is  seen  to  be  a  thin  twisted 
ribbon,  something  like  a  dumb-bell  in  cross  section  (Fig. 
112).  The  best  grade  is  known  as  Sea  Island  cotton,  valued 
for  its  long,  strong  fiber,  which  is  used  in  the  best  grades  of 
fine  thread  and  for  mercerizing.  The  average  length  of 
a  cotton  fiber  is  1.6  inches  and  its  diameter  0.00064  inch. 
In  strength  it  comes  between  wool  and  silk,  but  it  is  not  as 
elastic  as  either. 

If  the  crude  fiber  is  treated  with  dilute  sodium  hydroxide, 
dilute  acid,  water,  and  then  with  alcohol,  all  of  the  impuri- 
ties are  removed,  and  a  soft,  pure  cellulose  remains.  This 
is  the  absorbent  cotton  of  the  household. 

Cotton  goods,  if  tightly  stretched  and  treated  with  con- 
centrated cold  sodium  hydroxide  for  a  short  time,  and  then 


320  CHEMISTRY   IN  THE   HOME 

well  washed  with  water,  gain  about  30%  in  strength  and 
acquire  a  luster  like  that  of  silk.  The  process  is  called 
mercerization,  and  the  product,  mercerized  cotton.  If  the 
process  is  well  done,  mercerized  cotton  can  scarcely  be  dis- 
tinguished from  silk. 

Linen.  The  flax  plant  gives  us  the  fiber  called  linen.  Its 
use  in  cloth  dates  back  even  earlier  than  the  use  of  cotton, 
for  mummy  cloths  of  linen  have  been  found  in  Egypt  that 
date  from  about  2000  B.C.  The  plant  grows  to  a  height  of 
about  40  inches,  and  it  is  the  stalk  that  yields  the  fiber.  In 
addition  we  obtain  linseed  oil  from  the  seeds. 

The  flax  stalks  are  placed  in  stagnant  water,  where  an 
active  fermentation  soon  starts.  This  allows  the  linen  fiber 
to  be  separated  from  the  other  plant  products  by  mechanical 
means.  The  length  of  the  linen  fiber  varies  from  three  feet 
to  a  few  inches.  It  is  smooth,  and  has  a  somewhat  silklike 
luster.  It  is  much  stronger  than  cotton.  As  it  is  a  much 
better  conductor  of  heat  than  cotton,  it  is  cool  when  used 
as  a  dress  material. 

Wool.  Wool  is  the  hair  of  sheep.  There  are  many 
varieties,  depending  on  the  variety  of  sheep  from  which  it 
is  obtained.  Cashmere  comes  from  the  Thibet  goat,  mo- 
hair from  the  Angora  goat,  and  alpaca  from  the  llama.  Not 
all  of  the  dress  goods  having  these  names  come  from  the 
proper  source,  as  the  peculiar  characteristics  can  be  imitated 
by  common  wool. 

All  wool  fibers  have  an  outer  layer  of  flattened  cells,  the 
edges  of  which  project  outward,  giving  a  saw  tooth  appear- 
ance under  the  microscope  (Fig.  112).  When  the  wool 
fibers  are  beaten  together,  this  peculiar  structure  causes 
them  to  interlock,  and  felt.  These  scales  are  small  and 
numerous.  In  mohair  there  are  2000  scales  to  the  inch. 


TEXTILES 


321 


Wool  fibers  are  from  1  to  8  inches  in  length.  Wool  is 
bleached  with  hydrogen  peroxide,  as  chlorine  attacks  the 
fiber.  Wool  is  readily  soluble  in  sodium  hydroxide,  which 
gives  us  an  easy  way  of  distinguishing  it  from  other  fibers. 
It  dyes  easily  and  the  colors  are  usually  fast. 

As  wool  is  comparatively  expensive,  old  worn  woolen 
cloth  is  picked  to  pieces,  woven  again  into  yarn,  and  used 
with  a  proportion  of 
new  wool  to  make 
cloth.  This  "shoddy" 
has  a  short  fiber,  is 
weak,  and  will-  not 
wear  as  well  as  new 
wool.  It  is  of  course 
cheaper. 

Much  of  the  "all 
wool  cloth "  of  com- 
merce contains  cotton. 
If  it  were  sold  for 
what  it  is,  the  cotton 
would  not  be  objec- 
tionable, for  the  partly 


• 


.  1  13.  -Testing  for  "all  wool."  The  ends 
of  two  pieces  of  cloth  were  placed  in  hot 
dilute  sodium  hydroxide.  The  "all  wool" 
is  shown  on  the  left  ;  the  mixed  wool  and 

cotton  on  the  right. 


1,1  i 

cotton    cloth    can    be 

produced  more  cheaply 

than  the  all  wool.     It  is  not  as  warm  as  wool,   and  the 

two  materials  shrink  differently,   so  that  it  must  be  used 

with  care.     It  is  a  simple  matter  to  detect  the  fraud,  for 

if  such  a  cloth  is  placed  in  hot  dilute  sodium  hydroxide  the 

wool  will  dissolve,  while  the  cotton  will  remain  (Fig  113). 

Silk.  Silk  is  obtained  from  the  cocoon  of  the  silkworm. 
The  cocoons  are  heated  to  70°  C.,  which  kills  the  worm.  The 
silk  is  then  unreeled,  the  silk  fibers  from  several  cocoons 


322  CHEMISTRY   IN   THE   HOME 

twisted  together,  and  thus  a  silk  thread  is  obtained.  Only 
about  10%  of -the  weight  of  the  cocoons  is  obtained  as 
thread.  Five  per  cent  is  waste  silk  and  broken  threads 
used  in  spun  silk,  while  the  rest  is  waste. 


FIG.   114.  —  Silkworm,  cocoons,  chrysalis,  moth,  and  skein  of  silk. 

Silk  thread  has  a  beautiful  luster,  and  a  high  tensile 
strength,  64,000  pounds  per  square  inch.  The  average  diam- 
eter of  the  thread  is  about  0.0005  inch.  It  is  readily  dyed. 
The  fiber  is  round  and  smooth  (Fig  112).  It  is  easily  soluble 
in  concentrated  hydrochloric  acid,  or  in  basic  zinc  chloride, 
which  gives  us  an  easy  means  of  distinguishing  the  fiber. 


TEXTILES  323 

Artificial  silk.  Owing  to  the  beauty  of  silk,  and  its  high 
cost,  many  attempts  have  been  made  to  prepare  an  artificial 
silk.  There  are  several  products  on  the  market  that  go 
by  the  name  of  artificial  silk.  They  resemble  it  in  luster, 
but  have  an  entirely  different  composition.  There  are 
three  main  methods  of  preparing  them. 

Collodion  silk  is  made  by  dissolving  nitrated  cellulose 
in  a  mixture  of  alcohol  and  ether,  and  squirting  the  solution 
through  a  small  opening.  The  fine  thread  that  forms  is 
passed  through  water,  which  coagulates  it. 

Cuprate  silks  are  made  by  dissolving  cellulose  in  am- 
moniacal  copper  oxide.  The  solution  is  forced  through 
fine  glass  tubes  into  water,  which  coagulates  it.  The  cop- 
per is  removed  by  a  treatment  with  dilute  acid  and  the 
thread  dried. 

Viscose  silk  is  a  solution  of  mercerized  cellulose  in  sodium 
hydroxide  and  carbon  disulphide.  It  forms  a  thick  yellow- 
ish gelatinous  mass,  soluble  in  water.  This  solution  is 
forced  through  fine  openings  into  a  solution  of  ammonium 
sulphate  which  coagulates  the  fine  thread. 

All  of  these  artificial  silks  have  the  luster  of  silk,  but  are 
deficient  in  strength,  especially  when  wet.  They  are  difficult 
to  dye,  as  when  wet  they  are  so  weak  that  they  are  easily 
injured.  They  are  used  extensively  as  silk  substitutes,  as 
in  the  manufacture  of  braid,  neckties,  and  artificial  horsehair. 

SUMMARY 

Asbestos  is  a  silicate  that  occurs  in  long  fibers.  It  is  used  in  mak- 
ing heat  insulation  cloth. 

Cotton  is  almost  pure  cellulose.  It  is  the  most  used  fiber  for  cloth 
and  thread; 

Linen  comes  from  the  flax  plant. 

Wool  is  obtained  from  sheep.     It  is  soluble  in  sodium  hydroxide. 

WEED    CHEMISTRY 21 


324  CHEMISTRY   IN   THE   HOME 

Silk  comes  from  the  silkworm.     It  is  soluble  in  hydrochloric  acid. 

Artificial  silk  is  made  by  dissolving  cellulose,  forcing  the  solution 
through  small  holes  to  produce  a  thread,  and  then  coagulating 
the  solution.  It  has  the  luster  of  silk,  but  is  weak,  especially 
when  wet. 

Exercises 

1.  How  is  felt  made,  and  what  causes  the  fibers  to  stick  together? 

2.  What  simple  test  will  distinguish  wool  from  cotton? 

3.  What  is  shoddy? 

4.  Would  the  fibers  in  rhubarb  be  suitable  for  weaving  a  cloth? 
Explain. 

5.  Paper  can  be  made  waterproof.     Why  is  this  material  not  a 
suitable  dress  goods? 


CHAPTER  XXVII 
LAUNDRY    CHEMISTRY 

General  methods  of  removing  stains.  To  remove  a  stain 
from  cloth,  without  injury  to  it,  is  often  a  difficult  matter. 
The  knowledge  gained  in  your  study  of  chemistry  will  help 
you,  for  when  you  know  the  properties  of  the  substance 
causing  the  stain,  you  can  often  tell  what  means  to  use  to 
remove  it  with  certainty  and  safety. 

The  general  methods  of  removing  a  stain  are :  to  dissolve 
it,  to  absorb  it,  to  bleach  it,  or  to  neutralize  it.  Many 
delicate  colors  are  altered  or  destroyed  by  the  chemicals 
used  to  remove  stains.  If  a  small  piece  of  the  goods  can 
be  had,  it  is  well  to  try  the  effect  of  the  reagent  you  expect 
to  use  on  it,  so  that  you  may  guard  against  using  anything 
that  will  change  the  color  of  the  fabric. 

Removing  stains  by  solution.  The  safest  method  to  try 
first  is  solution.  The  solvent  to  be  used  will  of  course  de- 
pend on  the  stain  to  be  removed.  Water  will  dissolve 
such  substances  as  sugar,  gum,  and  many  salts.  Always 
use  cold  water  first,  and  plenty  of  it.  A  good  way  is  to  hold 
the  stain  under  the  cold  water  faucet,  and  allow  the  water 
to  flow  through  it.  After  most  of  the  stain  has  been  washed 
out,  warm  water  may  be  used  to  complete  its  removal.  To 
remove  a  stain  takes  time.  In  bleaching  cotton  sheeting 
the  manufacturer  takes  more  than  a  day  to  complete  the 
bleach.  Do  not  expect  water,  or  any  other  solvent,  to 

325 


326  CHEMISTRY   IN  THE   HOME 

remove  a  stain  instantly.  The  addition  of  soap  to  the 
water  will  often  help.  The  soap  forms  an  emulsion  with 
the  staining  material,  and  aids  its  removal. 

Alcohol  is  another  common  solvent  that  will  remove 
many  stains  caused  by  organic  substances.  Grass  stains 
readily  dissolve  in  alcohol. 

Grease  is  soluble  in  benzine,  naphtha,  gasoline,  and  benzol. 
While  all  of  these  will  readily  dissolve  the  grease,  their 
use  is  dangerous,  as  they  are  all  inflammable  materials. 
Fires  have  been  caused  by  rubbing  a  silk  waist  in  gasoline. 
The  friction  of  the  silk  sometimes  generates  tiny  electric 
sparks,  which  set  fire  to  the  gasoline,  and  a  disastrous  fire 
results.  Carbon  tetrachloride,  CC14,  will  dissolve  grease; 
it  is  cheap  and  noninflammable.  It  should  be  used  instead 
of  gasoline.  Carbona  is  largely  carbon  tetrachloride. 

Fresh  paint  is  easily  removed  by  carbon  tetrachloride  or 
turpentine.  After  paint  has  dried,  it  must  be  softened, 
by  soaking  it  in  amyl  acetate  or  pine  tar  oil,  before  it  can 
be  removed.  Varnish  is  a  solution  of  gums  in  either  alcohol 
or  oil.  If  a  spirit  varnish  is  to  be  removed,  alcohol  will 
dissolve  it.  If  an  oil  varnish  is  to  be  removed,  gasoline 
will  dissolve  it.  Ether  and  chloroform  are  other  solvents 
that  are  sometimes  useful. 

When  using  any  solvent,  you  must  remember  that  you 
are  dissolving  the  stain  and  forming  a  solution.  If  this 
solution  is  not  removed  from  the  fabric,  you  have  not  re- 
moved the  stain,  but  spread  it.  If,  starting  at  the  center 
of  the  spot,  you  rub  a  grease  spot  with  a  little  gasoline, 
the  grease  dissolves,  the  solution  spreads,  and  you  have  a 
ring  of  grease.  To  avoid  this,  start  at  the  edge  of  the  spot, 
and  work  toward  the  center.  Use  plenty  of  solvent,  and  as 
this  dissolves  the  grease,  remove  it,  and  replace  it  with  fresh. 


LAUNDRY    CHEMISTRY  327 

Removing  stains  by  absorption.  Grease  spots  can  also 
be  removed  by  absorption.  Mix  gasoline  with  talc  or 
starch  to  a  thick  paste,  and  place  this  over  and  under  the 
spot.  Capillary  action  will  draw  the  grease  solution  up 
into  the  talc.  When  dry,  brush  off  the  talc,  and  repeat 
if  necessary.  Blotting  paper  may  be  used  in  the  same  way. 
Place  a  piece  of  blotting  paper  over  and  under  the  spot, 
and  press  with  a  warm  iron.  The  grease  will  be  drawn 
into  the  paper. 

Necessity  of  using  a  suitable  solvent.  The  solvent  must 
be  suited  to  the  material  to  be  removed.  You  know  that 
iron  oxide  is  insoluble  in  all  of  the  solvents  that  have  been 
mentioned  so  far.  It  is  then  useless  to  try  to  remove 
iron  rust  with  any  of  them.  You  must  find  a  solvent  for 
iron  rust  before  you  can  remove  it  by  solution.  Acids  will 
dissolve  rust,  but  strong  acids  are  likely  to  injure  the  cloth. 
An  acid  must  be  selected  that  will  do  as  little  harm  as  possible, 
and  used  weak. 

The  acid  that  we  select  depends,  too,  upon  the  fabric. 
Silk  is  soluble  in  hydrochloric  acid.  Obviously  hydrochloric 
acid  cannot  be  used  on  silk.  A  weak  solution  of  oxalic 
acid  may  be  used.  On  cotton  or  linen  cloth,  weak  hydro- 
chloric acid  will  remove  the  rust  more  quickly.  After  the 
acid  has  served  its  purpose,  it  must  be  carefully  removed, 
or  it  will  injure  the  clot^h. 

Removing  acid  stains.  Since  most  anilin  dyes  are  in- 
dicators, a  drop  of  either  acid  or  alkali  will  change  their 
color.  The  remedy  is  to  neutralize.  If  lemonade  spilled 
on  a  silk  skirt  changes  its  color,  a  drop  of  dilute  ammonia 
will  restore  the  color,  for  the  change  produced  by  the  lemon 
was  due  to  the  acid  that  it  contained.  In  the  same  way, 
washing  soda  will  alter  colors.  A  few  drops  of  a  dilute  acid 


328  CHEMISTRY   IN  THE  HOME 

will  restore  them.  Do  not  forget  to  wash  out  the  materials 
used. 

Bleaching  with  Javelle  water.  Mildew  cannot  be  dis- 
solved. We  must  resort  to  another  method  to  remove  it. 
One  simple  way  is  to  bleach  it.  A  weak  solution  of  Javelle 
water 1  may  be  used.  The  mildewed  cloth  is  soaked  in 
weak  Javelle  water,  rubbed  well,  and  allowed  to  remain 
until  the  mildew  is  oxidized.  The  cloth  is  then  well  washed. 
Many  stains  caused  by  anilin  dyes  can  also  be  oxidized  by 
the  use  of  Javelle  water.  Chlorine  must  not  be  used  on 
either  wool  or  silk. 

Bleaching  with  sulphur  dioxide.  Straw  hats  that  have 
turned  yellow  may  be  bleached  with  sulphur  dioxide.  The 
hat  is  first  scrubbed  with  soap  and  water  to  remove  dirt, 
and,  while  still  wet,  hung  up  in  an  inverted  barrel.  A  little 
sulphur  is  burned  under  the  barrel.  The  sulphur  dioxide 
produced  will  bleach  the  straw. 

Bluing  clothes.  After  clothes  have  been  washed  they 
commonly  have  a  slight  yellow  tinge.  They  may  be  bleached 
by  the  action  of  dew  and  sunlight.  If  the  clothes  are  spread 
on  the  grass,  and  allowed  to  remain  some  time,  they  will  be 
bleached  to  a  pure  white.  Most  city  dwellers  find  it  im- 
possible to  do  this,  and  bluing  is  resorted  to.  The  slight 
blue  tinge  given  to  the  clothes  neutralizes  their  yellow  tinge, 
and  they  seem  to  be  pure  white. 

A  number  of  different  substances  are  used  for  bluing. 
Formerly  indigo  was  used.  As  it  is  insoluble  in  water,  a 
lump  of  indigo  was  tied  in  a  cloth  and  swished  through  the 
water.  This  left  indigo  in  suspension.  If  care  was  used, 
this  was  satisfactory,  but,  if  the  bluing  water  was  allowed 
to  stand,  the  indigo  settled,  and  the  clothes  were  streaked. 
1  See  the  laboratory  manual  for  its  preparation. 


LAUNDRY    CHEMISTRY  329 

Ultramarine  is  now  used  as  a  substitute  for  indigo.  Its 
action  is  the  same  as  that  of  indigo.  Reckitt's  blue  belongs 
to  this  class  of  insoluble  blues. 

Prussian  blue  is  used  as  a  cheap  substitute  for  ultramarine. 
This  has  the  disadvantage  that  if  the  goods  are  not  well 
rinsed  before  the  blue  is  used,  it  will  decompose  and  produce 
iron  rust  on  the  clothes.  It  is  not  as  satisfactory  as  either 
indigo  or  ultramarine. 

Soluble  washing  blues  are  largely  aniline  colors.  They 
are  easy  to  use,  as  they  do  not  settle,  and  give  the  clothes  a 
satisfactory  color.  Dyes  are  used  that  do  not  permanently 
stain  the  fibers. 

The  use  of  soap.  Soap  is  used  for  ordinary  cleansing  of 
clothes.  A  good  grade  of  laundry  soap  should  not  contain 
too  large  a  percentage  of  water,  and  no  free  fat.  The  yellow 
laundry  soaps  are  made  in  part  from  rosin.  This  is  hardly 
an  adulteration,  as  rosin  soap  is  a  detergent  and  lathers 
freely.  It  tends,  however,  to  make  the  clothes  yellow.  The 
presence  of  free  alkali  is  objectionable,  as  it  is  harmful  to 
clothing  and  to  the  skin. 

Just  how  soap  aids  in  the  removal  of  dirt  is  a  disputed 
question.  Its  action  is  probably  both  chemical  and  me- 
chanical. Its  action  is  largely  due  to  the  fact  that  soap 
solutions  will  break  up  and  emulsify  the  fatty  substances 
that  hold  the  dirt  on  the  clothes. 

Washing  powders.  Washing  soda  acts  upon  grease  and 
softens  hard  water.  A  mixture  of  washing  soda  and  pow- 
dered soap  makes  up  the  majority  of  the  washing  powders. 
It  is  usually  cheaper  to  use  washing  soda  and  soap  than 
these  prepared  powders.  When  crystals  of  washing  soda 
are  used,  they  should  be  dissolved  in  water  and  a  little  of 
the  solution  mixed  well  with  the  wash  water. 


330  CHEMISTRY   IN  THE   HOME 

How  laundries  wash  clothes.  An  outline  of  the  method 
used  in  a  large  laundry  in  cleaning  collars  and  cuffs  will 
show  the  differences  between  commercial  and  home  methods. 
The  collars  are  marked  to  identify  them,  and  then  placed 
in  cold  water  for  five  minutes.  This  loosens  the  dirt,  and 
dissolves  some  albuminous  matters  that  would  be  coagulated 
if  the  collars  were  put  into  hot  water  first.  This  water  is 
then  run  off,  and  hot  water  and  soap  added,  also  washing 
soda  if  that  is  necessary.  The  water  is  gradually  heated 
to  the  boiling  point.  Twenty-five  minutes  are  allowed  for 
this  "  first  suds." 

The  dirty  water  is  run  off,  replaced  by  fresh,  and  a  small 
quantity  of  soap  added.  A  bleach  made  from  chloride  of 
lime  is  also  added.  This  "  second  suds  "  is  gradually  heated 
to  the  boiling  point. 

After  twenty-five  minutes  this  second  soapy  water  is 
run  off,  and  the  collars  rinsed  twice  with  hot  water.  Ten 
minutes  is  allowed  for  each  rinse.  A  third  rinse  containing 
acid  is  then  given.  The  object  of  the  acid  is  to  neutralize 
any  alkali  remaining  in  the  clothes,  as  this  would  destroy 
the  bluing  used. 

The  collars  are  then  blued,  rinsed  again,  and  starched. 
The  starch  used  is  a  thin  boiling,  cornstarch,  and  is  rubbed 
into  the  collars  by  machinery.  The  excess  of  starch  is 
then  rubbed  off,  first  with  the  hand,  and  then  with  cheese- 
cloth, and  the  collars  dried.  They  are  then  dampened  and 
ironed. 

The  main  objection  to  such  laundries  is  the  bleach  em- 
ployed. This  is  often  used  too  strong,  so  as  to  hasten  the 
whitening  of  the  clothes.  As  a  result,  the  cloth  is  made 
very  tender,  and  is  easily  torn. 


LAUNDRY    CHEMISTRY  331 

SUMMARY 

Stains  are  removed  by  solution,  absorption,  bleaching,  and  neu- 
tralization. 

Laundry  blues  are  indigo,  ultramarine,  and  Prussian  blue.  Soluble 
blues  are  aniline  colors. 

Washing  powders  are  mixtures  of  soap  and  washing  soda. 

Exercises 

1.  How  would  you  remove  a  grass  stain  from  a  white  skirt? 

2.  Why  does  the  juice  of  grapefruit  stain  colored   goods,  and 
how  would  you  remove  the  stain? 

3.  Why  do  you  put  clothes  to  soak  in  cold  water? 

4.  What  is  "  dry  cleaning  "? 

5.  How  would  you  clean  your  straw  hat? 

6.  Why  are  blued  clothes  sometimes  streaky? 

7.  Are  yellow  soaps  economical? 


CHAPTER  XXVIII 
THE    CHEMISTRY    OF    COOKING 

Advantages  of  cooked  food.  It  is  possible  to  sustain 
life  on  raw  food,  but  all  mankind,  including  even  the  savage 
races,  has  found  that  cooking  renders  many  foods  more 
palatable. 

Food  is  cooked  for  many  reasons.  The  flavor  may  be 
improved,  as  in  the  case  of  meats.  The  tough  fibers  are 
softened,  allowing  easy  digestion,  as  in  the  case  of  vegetables. 
Any  parasites  present  are  killed,  thus  making  the  food  more 
healthful. 

Cooking  coagulates  the  protein  present.  Dry  heat  con- 
verts starch  into  dextrin  and  glucose.  Moist  heat  swells 
the  starch  granules  and  causes  them  to  break  open.  Sugars 
are  changed  to  caramel,  and  fats  decompose.  All  these 
changes  cause  alterations  in  the  flavor  of  the  food,  and  often 
produce  savory  odors  that  arouse  the  appetite. 

How  to  cook  protein.  Boiling  an  egg  is  perhaps  the 
simplest  operation  in  cooking,  and  yet  if  you  understand 
how  to  do  this,  you  will  understand  the  fundamental  prin- 
ciples underlying  the  cooking  of  all  meats.  Albumin  when 
heated  to  158°  F.  coagulates.  If  the  raw  egg  is  put  into 
boiling  water,  the  outside  layer  of  albumin  quickly  becomes 
hard  and  tough,  while  the  inside  of  the  egg  is  still  raw.  If, 
however,  the  egg  is  placed  in  cold  water,  and  gradually 
heated,  it  becomes  hot  all  through,  the  albumin  coagulates 

332 


THE   CHEMISTRY   OF   COOKING  333 

throughout  to  a  jellylike  mass,  and  the  egg  is  more  palatable 
and  digestible. 

In  boiling  meats,  if  the  meat  is  put  into  cold  water,  the 
albuminoids  and  extractives  dissolve,  and  pass  into  the  water. 
This  makes  the  water  rich,  but  leaves  the  meat  dry  and 
tasteless.  We  should  therefore  put  the  meat  into  boiling 
water.  This  will  coagulate  the  albumin  on  the  outside  and 
prevent  the  escape  of  the  juice.  If  we  wish  to  extract  the 
juice,  as  in  making  soups  and  beef  tea,  we  should  cut  the 
meat  into  small  pieces,  put  these  into  cold  water,  and  heat 
them  slowly. 

Simmering.  Simmering,  which  is  cooking  at  a  tempera- 
ture of  185°  F.,  makes  meat  tender.  The  meat  is  first  put 
into  boiling  water  to  coagulate  the  outside,  and  then  the 
temperature  lowered.  This  keeps  the  fibers  tender,  but  the 
meat  must  of  course  be  cooked  for  a  longer  time. 

Fried  steak  has  ruined  many  a  farmer's  stomach,  but  the 
fault  is  not  in  frying,  but  in  the  way  in  which  it  is  done.  If 
a  steak  is  put  into  a  cold  frying  pan,  with  some  fat,  and  then 
heated,  the  fat  is  drawn  up  between  the  fibers  of  the  meat. 
Each  individual  fiber  is  covered  with  a  layer  of  fat,  and  a 
greasy,  dry,  indigestible  mass  results.  If  the  steak  had 
been  put  on  a  very  hot  frying  pan,  the  outside  ends  of  the 
fibers  would  have  been  seared,  and  a  result  almost  equal  to 
broiling  obtained. 

Deep-fat  frying.  Frying  by  immersion  in  deep,  hot  fat 
is  a  common  method  of  cooking  many  foods.  Fat  does  not 
boil,  but  when  heated  to  a  temperature  considerably  above 
the  boiling  point  of  water,  it  smokes.  It  is  then  almost 
at  its  kindling  temperature,  and  care  must  be  taken  that 
it  does  not  catch  on  fire.  As  smoking  fat  is  far  above  212°  F., 
water  thrown  into  it  instantly  changes  into  steam.  This 


334  CHEMISTRY   IN  THE   HOME 

causes  a  slight  explosion,  and  hot  fat  is  thrown  around. 
It  is  for  this  reason  that  whatever  we  wish  to  fry  should 
be  dry. 

Fried  foods  are  greasy  because  cooks  do  not  keep  the  fat 
hot  enough.  When,  as  in  the  home,  a  small  quantity  of 
fat  is  used,  to  throw  a  large  handful  of  potatoes  into  it  cools 
the  fat  so  much,  that,  instead  of  a  crust  forming  on  the 
outside  of  the  potatoes,  which  prevents  the  entrance  of  the 
fat,  the  grease  sinks  in  between  the  starch  grains.  Naturally 
a  greasy,  indigestible  mass  is  the  result. 

Rule  for  cooking  meat.  There  are  only  two  things  to 
remember  in  cooking  meats.  If  you  wish  to  keep*  the  juice 
in,  heat  quickly  to  coagulate  the  outside.  If  you  wish  to 
extract  the  juice,  heat  slowly,  and  keep  the  temperature 
below  185°  F. 

Cooking  vegetables.  The  chief  advantage  gained  in 
cooking  vegetables  is  in  making  them  more  digestible. 
Heating  swells  the  starch  granules  and  they  burst,  tearing 
apart  the  cellular  structure  in  which  they  are  imbedded. 
The  digestive  juices  are  then  able  to  get  at  the  starch  and 
digest  it. 

Vegetables  are  best  placed  in  plenty  of  boiling  water  if 
we  wish  to  retain  their  flavor.  When  we  wish  to  extract 
part  of  the  flavor,  as  in  the  case  of  onions,  they  are  best 
placed  in  cold  water,  and  then  brought  slowly  to  a  boil. 

A  fallacy  of  cooks.  One  very  common  mistake  of  the 
cook  is  in  thinking  that  hard  boiling  heats  water  to  a  higher 
temperature  than  slow  boiling.  You  know  that  water  boils 
at  212°  F.  Whether  it  is  boiling  furiously,  or  is  only  just 
boiling,  makes  no  difference.  It  is  impossible  to  raise  its 
temperature.  To  boil  potatoes  hard,  then,  is  to  waste 
fuel. 


THE   CHEMISTRY   OF   COOKING  335 

SUMMARY 

Cooking  food  makes  it  easier  to  digest,  more  palatable,  and  safe. 
Cooking  meats :   To  keep  meat  juices  in,  place  the  meat  first  in 

boiling  water.     To  extract  meat  juices,  place  the  meat  in  cold 

water  and  heat  slowly. 
Simmering  is  cooking  by  heating  in  water   at   a   temperature   of 

185°  F. 
Temperature  of  boiling  water.     Water  has  the  same  temperature, 

whether  boiling  slowly  or  furiously.     In  an  open  vessel  at 

sea  level  it  is  212°  F. 

Exercises 

1.  How  would  you  hard-boil  an  egg? 

2.  How  would  you  prepare  beef  tea? 

3.  Why  do  thin  pieces  of  potato  swell  when  dropped  into  very 
hot  fat? 

4.  Why  is  the  meat  left  in  preparing  soup  so  tasteless  ? 

5.  In  cooking  vegetables  should  they  be  put  first  into  hot  or 
cold  water?     Why? 

6.  What  causes  greasy  doughnuts? 

7.  Why  is  toast  rather  than  bread  given  to  invalids? 


CHAPTER   XXIX 


CALCIUM    AND    ITS    COMPOUNDS 

The  metal  calcium.  The  element  calcium  is  a  hard,  sil- 
very metal,  that  has  no  commercial  use.  Calcium  is  never 
found  free  in  nature,  for,  like  sodium,  it  oxidizes  on  exposure 

to  moist  air.  It  is 
easily  prepared  by 
the  electrolysis  of  the 
fused  chloride.  Its 
compounds  are  impor- 
tant, forming  about 
one  fifteenth  of  the 
bulk  of  the  earth. 
You  are  already 
familiar  with  some  of 
them,  as  lime  and 
marble. 

Calcium  carbonate. 
Calcium  carbonate, 
CaCOs,  occurs  in  the 
most  varied  forms, 
sometimes  beautifully 
crystallized,  and  sometimes  as  an  amorphous  rock.  Marble, 
limestone,  and,  the  shells  of  shellfish  are  almost  entirely 
calcium  carbonate.  Chalk  is  the  shell  remains  of  a  micro- 
organism and  is  almost  pure  calcium  carbonate.  When 

336 


FIG.  115.  —  Limestone,  showing  its  shell  origin. 


••• 


CALCIUM   AND    ITS   COMPOUNDS  337 

washed  and  puri- 
fied, it  is  called  whit- 
ing, and  is  used  for 

calcimine.       Whit-  *% 

ing  mixed  with  lin-  fcl     ' 

seed  oil  forms  putty. 
Pearls  are  calcium 
carbonate,  as  is  also 
coral.  When  pure, 
it  occurs  in  large, 
transparent  crys- 
tals,  called  Iceland 
spar  and  dogtooth 

FIG.   116.  —  Dogtooth  spar. 

All    varieties    of 

calcium  carbonate  are  easily  acted  on  by  acids,  carbon  di- 
oxide being  given  off. 

CaC03  +  2  HC1  -*  CaCl2  +  H2O  +  CO2  f 

This  serves  to  distinguish  it  from  other  white  rocks. 

Marble.  Marble  is  insoluble  in  water,  and  it  is  an  inter- 
esting question  how  such  animals  as  corals  can  obtain  the 
calcium  carbonate  necessary  to  form  their  skeletons.  If  you 
have  ever  noticed  the  marble  slab  under  the  faucet  of  the 
soda  fountain,  you  will  have  seen  that  it  is  very  badly  worn, 
even  though  the  rest  of  the  soda  fountain  is  new.  These 
slabs  have  to  be  renewed  every  year.  This  gives  us  a  clue. 
Carbon  dioxide  when  it  dissolves  in  water  forms  an  acid 
called  carbonic  acid,  and  marble  is  soluble  in  this  acid,  form- 
ing calcium  bicarbonate. 

H20  +  C02  ->  H2C03 

H2CO3  +  CaCO3->CaH2(C03)2 


338 


CHEMISTRY   IN   THE   HOME  ' 


FIG.   117.  — How  caves  are  formed  by  water 
containing  carbon  dioxide. 


When  it  rains,  the 
rain  water  dissolves 
carbon  dioxide  from 
the  air,  and  forms  a 
weak  solution  of  car- 
bonic acid.  This  sinks 
into  the  ground,  and, 
if  it  runs  over  marble, 


will  dissolve  it,  forming  a  solution  of  calcium  bicarbonate. 
This  runs  to  the  sea,  and  it  is  from  this  source  that  the  coral 
animals  and  the  shellfish  obtain  the  calcium  carbonate 
necessary  for  their  growth. 

How  caves  are  formed.  This  dissolving  of  marble  or  lime- 
stone leaves  cavities 
in  the  ground.  These 
are  caves,  such  as  the 
Mammoth  cave  of 
Kentucky.  As  mar- 
ble varies  in  hard- 
ness, some  parts  of 
it  will  be  more  easily 
dissolved  than  others, 
hence  the  winding 
passages,  the  large 
rooms,  and  low  chan- 
nels found  in  caves. 

If  water  containing 
calcium  bicarbonate 
trickles  over  the  roof 
of  a  cave,  and  evapo- 
rates, calcium  car- 
bonate is  left.  As 


FIG.   118.  — Stalactites  and  stalagmites  in 
Mammoth  cave. 


CALCIUM   AND   ITS   COMPOUNDS  339 

water  continues  to  flow  in  and  evaporate,  a  stone  "  icicle/' 
called  a  stalactite,  forms.  A  slight  wind  blowing  through  the 
cave  will  force  the  water  to  one  side  of  the  stalactite,  or  a 
grain  of  sand  will  divert  its  course.  In  such  ways  the  most 
curious  stalactitic  forms  arise. 

If  more  water  trickles  down  the  stalactite  than  can  evapor- 
ate, some  drops  to  the  floor  of  the  cave.  Here  it  forms  a  pool 
that  slowly  evaporates  and  deposits  a  mound  that  slowly 
grows  upward.  This  is  a  stalagmite.  When  a  stalactite 
and  a  stalagmite  meet,  they  form  a  column. 

As  the  water  occasionally  contains  iron  and  mud  as  im- 
purities, these  growths  are  sometimes  white,  and  sometimes 
brown,  pink,  or  dark  gray.  It  requires  only  a  little  imagina- 
tion to  see  in  these  grotesque  growths  the  Organ,  the  Bishop's 
Chair,  and  other  fan- 
ciful objects  that  the 
guide  points  out  to 
you. 

Coral  rock.  Coral 
animals  cannot  live 
out  of  water,  so  when 
they  have  carried 
their  skeletons  to 
within  a  few  feet  of 
the  surface  of  the 

Fi<;.    119. —  Coral. 

ocean  they  stop  build- 
ing. Storms  break  off  the  top  portion  of  the  coral  rock,  grind 
it  to  powder,  and  this  fills  up  the  cracks  of  the  coral.  Floating 
vegetable  matter  drifts  on  to  the  coral  and  is  caught,  shells  and 
seaweeds  are  washed  up,  and  finally,  as  a  result  of  all  these 
agencies,  a  land  area  is  formed  above  the  surface  of  the  ocean. 
Birds  then  use  this  as  a  resting  place  and  deposit  seeds  there, 

WEED    CHEMISTRY 22 


340  CHEMISTRY   IN  THE  HOME 

or,  perhaps  a  floating  coconut  strands  on  the  shore.  Soon 
vegetation  starts  growing,  and  we  have  a  verdant  coral  isle. 

If  you  have  been  in  Florida  and  noticed  the  rock  (coquina) 
of  which  St.  Augustine  is  largely  built,  you  know  that  it  is 
composed  of  broken  shells.  In  time,  these  broken  shells 
become  compact,  and  limestone  results.  This  completes 
the  cycle,  that  will  recommence  when  rain  water  falls  on  the 
limestone  and  again  dissolves  it.  All  marble  and  limestone 
deposits  are  the  remains  of  life.  In  many  specimens  of 
limestone  you  can  make  out  faint  traces  of  the  shells  from 
which  it  was  built. 

Gypsum.  Gypsum  is  one  of  the  common  white  minerals 
found  in  many  parts  of  the  United  States.  It  is  so  soft  that 
it  can  be  scratched  by  the  finger  nail.  When  pure  it  is  white, 
but  it  is  often  colored  red,  yellow,  or  brown,  by  the  presence 
of  small  amounts  of  impurities.  Chemically  it  is  calcium 
sulphate,  CaSO4,  containing  two  molecules  of  water  of  crys- 
tallization, CaSO4  •  2  H2O.  When  heated,  gypsum  loses  most 
of  this  water  of  crystallization  and  is  converted  into  amor- 
phous calcium  sulphate.  This,  when  mixed  with  water, 
combines  with  it,  crystallizes,  and  forms  gypsum  once  more. 

Plaster  of  Paris.  Anhydrous  gypsum  is  ground  to  a  fine 
powder  called  plaster  of  Paris,  because  it  was  first  made  near 
the  city  of  Paris.  This  is  used  to  make  plaster  objects  by 
1  mixing  it  with  enough  water  to  form  a  thick  mud,  and  pouring 
into  molds.  The  water  combines  with  the  calcium  sulphate, 
forming  gypsum,  the  mass  sets  or  becomes  hard,  and  a 
plaster  cast  is  thus  obtained.  Large  amounts  of  plaster  of 
Paris  are  used  in  making  plaster  casts,  stucco,  the  final  finish 
of  walls,  and  the  outside  of  such  temporary  buildings  as  are 
often  erected  at  seaside  resorts. 

Gypsum  is  slightly  soluble  in  water,  one  part  of  gypsum 


CALCIUM   AND   ITS   COMPOUNDS 


341 


limestone 


requiring  500  parts  of  water  to  dissolve  it  at  ordinary  tem- 
peratures. Since  gypsum  is  a  common  mineral,  it  follows 
that  in  many  parts  of  the  country  the  spring  waters  will 
contain  gypsum  in  solution. 

Making  of  quicklime.  When  heated  to  a  red  heat,  marble 
decomposes,  and  gives  off  carbon  dioxide,  leaving  calcium 
oxide,  called  quicklime. 

CaCO3  +  heat  ->  CaO  -f  CO,  | 

The  making  of  quicklime  is  carried  out  commercially  by 
heating  marble  or  limestone  in  large  furnaces  called  lime 
kilns.     The  product  is  a  white  solid  used  in  making  mortar. 
The    kiln    is    filled    with 
limestone.     The  hot  gases 
from     the    furnace    con- 
stantly   mingle    with    it. 
At  about  1800°  F.  carbon 
dioxide  escapes  from  the 
limestone  and  lime  results. 
This  is  drawn  from   the 
bottom  of  the  kiln  from 
time  to  time. 

Slaked  lime.  When 
water  is  added  to  quick- 
lime, it  swells  up,  and  is 
changed  to  slaked  lime  or 
calcium  hydroxide. 

CaO  +  H2O  ->  Ca(OH)2 

A  large  amount  of  heat 
is  developed  during  this 
chemical  change.  It  is  not  FIG.  120.  —  A  lime  kiln. 


342  CHEMISTRY  IN  THE   HOME 

uncommon  for  a  barge  carrying  quicklime  to  catch  on  fire,  if, 
by  chance,  a  little  water  reaches  the  lime.  It  is  a  dangerous 
chemical  and  must  be  stored  with  care. 

Self-heating  canned  soups  have  been  made  by  taking  ad- 
vantage of  this  heating  effect.  A  sealed  pint  can  of  soup 
is  placed  in  a  quart  tin  can,  and  the  space  between  the  two  is 
filled  with  quicklime.  The  outer  can  is  then  sealed.  When 
the  soup  is  to  be  used,  holes  are  punched  in  the  outer  can 
and  water  poured  in.  The  lime  slakes,  and  the  soup  be- 
comes hot.  This  method  of  heating  is  of  use  to  balloonists, 
who  dare  not  use  a  fire,  lest  the  gas  contained  in  the  bal- 
loon catch  on  fire. 

Mortar  and  plaster.  Mortar  is  made  by  mixing  quicklime, 
water,  and  sharp  sand.  This  mixture  is  placed  between 
bricks  to  hold  them  together.  The  calcium  hydroxide  that 
is  produced  absorbs  carbon  dioxide  from  the  air,  and  changes 
back  to  marble. 

Ca(OH)2  +  CO2  ->  CaCO3  +  H2O 

In  time  the  mortar  becomes  as  hard  as  the  bricks  themselves. 

The  plaster  used  to  cover  the  laths  nailed  on  walls  is 
mortar  to  which  some  hair  has  been  added  to  increase  its 
tenacity.  Newly  built  houses  are  unhealthful  because  both 
the  mortar  and  plaster,  although  seemingly  dry,  are  giving 
off  large  quantities  of  water.  This  makes  the  house  damp. 
Then,  too,  the  hair  in  the  damp  plaster  slowly  decomposes, 
and  this  is  unpleasant. 

Limewater.  Calcium  hydroxide  is  slightly  soluble  in  water. 
The  filtered  solution  is  called  limewater.  It  is  used  as  a  test 
for  carbon  dioxide,  and  is  mixed  with  milk  to  make  it  more 
digestible  for  invalids.  It  must  be  protected  from  the  air,  as 
otherwise  it  absorbs  carbon  dioxide  and  becomes  worthless. 


CALCIUM   AND   ITS   COMPOUNDS  343 

As  calcium  hydroxide  is  a  base,  and  is  cheap,  chemists 
use  it  in  large  amounts  to  neutralize  acids.  It  is  also  used 
in  the  manufacture  of  sodium  hydroxide,  in  bleaching  powder, 
and  in  purifying  illuminating  gas. 

Calcium  phosphate.  Calcium  phosphate,  Ca3(PO4)2,  is  the 
main  mineral  constituent  of  our  bones.  It  occurs  as  a  rock 
in  Canada,  Florida,  South  Carolina,  and  other  places.  The 
phosphorus  in  this  rock  is  valuable  as  a  fertilizer,  but  must 
be  changed  into  a  soluble  form  before  plants  can  use  it.  This 
is  done  by  treating  the  phosphate  with  sulphuric  acid,  when 
calcium  superphosphate  is  formed. 

Ca3(PO4)2  +  2  H2SO4  ->  2  CaSO4  +  CaH4(PO4)2 

This  superphosphate  is  mixed  with  some  nitrogenous  material 
and  forms  a  commercial  fertilizer. 

Bleaching  powder.  Chloride  of  lime,  bleaching  powder, 
CaOCl2,  is  made  by  passing  chlorine  gas  over  layers  of  pow- 
dered slaked  lime.  It  is  a  white  powder  that  smells  feebly  of 
chlorine.  The  addition  of  an  acid  sets  free  chlorine,  as  you 
have  seen  in  your  laboratory  work. 

CaCl(OCl)  +  H2S04  ->  CaS04  +  HC1  +  HC1O 
HC1  +  HC1O  -*  H20  +  C12 

It  is  used  as  a  source  of  chlorine  and  for  disinfecting. 

Hard  waters.  When  water  containing  a  soluble  calcium 
salt  is  brought  into  contact  with  soap,  a  white  precipitate 
of  lime  soap  is  formed.  Such  water  is  called  hard  water. 
There  are  two  kinds,  temporary  and  permanent  hard  water. 

Temporary  hard  water  contains  calcium  bicarbonate.  It 
may  be  softened  by  heating,  which  drives  out  the  carbon 
dioxide,  leaving  calcium  carbonate  as  a  white  precipitate. 

CaH2(CO3)2  +  heat  -+  CaCO3 1  +  CO2  f  +  H2O 


344  CHEMISTRY   IN  THE  HOME 

When  large  quantities  of  temporary  hard  water  must  be 
softened,  heating  is  too  expensive.  Instead,  lime  is  added, 
and  the  water  allowed  to  stand  until  clear.  Exactly  the 
right  amount  of  lime  must  be  added,  as  otherwise,  the 
excess  of  lime  will  itself  make  the  water  hard.  This 
method  of  softening  can  only  be  carried  out  successfully 
by  a  chemist. 

CaH2(CO3)2  +  Ca(OH)2  -+  2  CaCO3 1  +  2  H2O 

Permanent  hard  water  contains  calcium  sulphate,  or  some- 
times magnesium  sulphate  or  chloride.  It  can  be  softened 
by  adding  sodium  carbonate. 

CaSO4  +  NaaCOa  ->  CaCO3 1  +  Na2SO4 

Disadvantages  of  hard  water.  Hard  water  used  in  the 
home  has  several  disadvantages.  It  deposits  a  fur  on  the  in- 
side of  teakettles,  and  this  deposit,  being  a  nonconductor 
of  heat,  renders  it  difficult  to  heat  the  water. 

In  washing,  large  amounts  of  soap  must  be  used  to  precipi- 
tate lime  soap,  and  this  is  waste,  not  only  on  account  of  the 
soap  that  is  consumed,  but  because  the  lime  soap  is  sticky 
and  soils  the  clothes. 

Hard  water  is  also  objectionable  in  industries.  It  forms 
a  scale  in  boilers,  and  interferes  with  many  chemical  proc- 
esses. 

How  hardness  is  measured.  The  hardness  of  water  is 
always  given  in  degrees.  One  degree  is  one  grain  of  calcium 
carbonate,  or  its  equivalent  in  other  salts,  in  one  gallon  of 
water  (58,333  grains).  The  higher  the  degree  of  hardness, 
the  worse  the  water  for  domestic  use.  One  hundred  gallons 
of  water,  of  ten  degrees  hardness,  requires  about  one  pound 
of  soap  to  soften  it. 


CALCIUM   AND   ITS   COMPOUNDS  345 

SUMMARY 

Calcium  is  a  silvery  white  metal  that  oxidizes  on  exposure  to  moist 

air. 
Calcium  carbonate   exists  as  marble,   limestone,   coral,   shells  of 

shellfish,  pearls.     Gypsum  is  calcium  sulphate.     Heated  and 

ground,  it  forms  plaster  of  Paris. 

Quicklime  is  calcium  oxide.     Slaked  lime  is  calcium  hydroxide. 
Mortar  is  a  mixture  of  quicklime,  sharp  sand,  and  water. 
Bleaching   powder  is  made   by   passing   chlorine  over  powdered 

calcium  hydroxide. 
Temporary  hard  water  contains  calcium  bicarbonate.     It  is  softened 

by  boiling  or  by  adding  slaked  lime. 
Permanent  hard  water  is  water  containing  calcium  sulphate,  or 

magnesium  sulphate  or  chloride.     It  is  softened  by  adding 

sodium  carbonate. 
Hardness  of  water  is  measured  in  degrees.     One  degree  is  one 

grain  of  calcium  carbonate,  or  its  equivalent  in  other  salts, 

in  one  gallon  of  water. 

Exercises 

1.  How  would  you  obtain  a  plaster  replica  of  a  medal? 

2.  How  should  putty  be  stored,  and  why  ? 

3.  Why  does  putty  harden? 

4.  If  you  breathe  through  limewater,  it  first  becomes  cloudy  and 
then  clears.     Why? 

6.   How  could  you  distinguish  between  a  temporary  and  a  perma- 
nent hard  water? 


CHAPTER  XXX 
DYES   AND   DYEING 

Usefulness.  Many  of  us  have  in  our  home  materials  that 
have  been  discarded,  not  because  of  wear,  but  because  the 
color  has  faded,  or  no  longer  goes  with  the  furnishings  of  a 
room.  In  many  such  cases  it  is  possible  with  a  little  care  to 
dye  the  article  at  home  so  that  it  again  becomes  useful. 
Dresses,  satin  slippers,  draperies,  curtains,  straw  hats,  and 
feathers,  all  may  be  done  as  well  at  home  as  by  a  professional, 
if  only  care  and  a  little  chemical  knowledge  are  used. 

Preliminary  precautions.  Before  dyeing  anything  it  must 
be  clean.  This  means  more  than  a  mere  surface  cleanliness. 
If  a  grease  spot  has  been  imperfectly  removed,  it  may  not 
show  on  the  goods,  but  it  will  prevent  the  even  action  of  the 
dye  and  cause  a  spot.  Perspiration  stains,  fruit  stains,  rust 
spots,  all  must  be  removed  if  we  are  to  have  a  perfect  result. 
It  is  well  to  remove  any  buttons,  especially  if  of  metal,  and 
any  bead  or  metal  trimming,  as  these  interfere  with  some  of 
the  dyes  used.  It  is  impossible  to  dye  a  light  color  over  a 
dark,  and  in  general  the  colors  produced  are  more  satisfactory 
on  white  cloth.  It  is  well  therefore  to  remove  as  much  of  the 
original  color  as  possible  before  attempting  to  re-dye.  Often 
boiling  in  two  changes  of  water  will  discharge  much  of  the 
original  color. 

Care  necessary.  First  select  a  suitable  dye.  This  means 
not  only  to  pick  out  a  dye  of  the  color  you  wish,  but  also  one 

346 


DYES  AND   DYEING  347 

that  will  be  suitable  for  the  material  used.  When  you  have 
studied  the  later  paragraphs  of  the  chapter,  you  will  under- 
stand how  to  pick  the  dye,  depending  on  whether  the  material 
is  vegetable  or  animal  fiber.  Special  care  must  be  used  in 
mixed  goods.  Many  dyes  do  not  take  on  cotton  as  well 
as  they  do  on  wool,  so  that  these  dyes  used  on  a  mixture  of 
wool  and  cotton  would  produce  a  mottled  effect. 

Having  selected  the  dye,  dissolve  it  in  a  little  water 
(assuming  it  to  be  one  of  the  common  aniline  dyes),  and  filter 
through  cloth  to  remove  any  undissolved  particles.  Dilute 
the  solution  to  the  required  volume  in  a  large  vessel  that 
will  stand  heat.  Do  not  use  iron  pots,  as  any  rust  will  prevent 
success,  and  the  iron  will  discolor  many  dyes.  Heat  the  dye 
until  almost  boiling  and  then  immerse  the  goods,  having  first 
wet  them  thoroughly.  This  is  important  and  is  often  over- 
looked. If  the  goods  are  not  kept  constantly  in  motion, 
different  parts  of  the  cloth  will  receive  different  amounts  of 
the  dye,  and  the  color  will  be  uneven,  or  not  "  level."  There- 
fore with  the  aid  of  two  sticks  lift  the  goods  and  move  them 
about  during  the  time  required  to  complete  the  dyeing. 
Most  dyes  take  best  at  the  boiling  temperature,  but  this  does 
not  mean  that  it  is  necessary  to  boil  them  furiously ;  simply 
keep  them  at  the  boiling  temperature.  The  shade  of  the 
goods  after  drying  is  generally  lighter  than  while  wet,  and 
some  experience  is  necessary  to  match  shades  exactly.  For 
this  reason,  and  because  of  the  uncertain  character  of  the 
fiber  in  some  goods,  it  is  well  to  dye  a  sample  first,  noting  the 
time,  etc.,  and  then  treating  the  main  bulk  of  goods  in  accord- 
ance with  the  experience  gained. 

To  finish,  rinse  in  cold  water  until  the  wash  water  is  color- 
less, then  dry  and  press.  Remember  especially  to  enter  the 
goods  wet,  not  to  hurry  the  operation,  not  to  try  to  dye  light 


348  CHEMISTRY   IN  THE  HOME 

colors  over  dark,  and  most  important  of  all  to  use  a  suitable 
dye. 

Obtaining  dyes.  The  coloring  power  of  the  artificial  dyes 
is  so  great  that  only  small  quantities  of  them  are  needed. 
They  can  be  bought  by  the  ounce  from  chemical  dealers 
costing  from  25  to  75  cents  an  ounce.  The  small  packages 
of  the  dyes  on  sale  under  various  trade  names  are  satisfactory, 
but  they  are  more  costly  in  proportion  to  the  amount  of  dye 
received. 

Fast  colors.  One  annoying  thing  about  colored  goods  is 
their  tendency  to  change  color.  The  fastness  of  colors  is 
measured  by  their  resistance  to  the  different  changing  agents. 
Thus  a  color  may  be  fast  to  light,  but  not  fast  to  washing, 
or  fast  to  washing  but  not  fast  to  perspiration.  The  only 
way  to  be  sure  that  any  given  piece  of  goods  will  meet  your 
requirements  is  to  try  it. 

An  easy  way  to  try  fastness  to  light  is  to  cut  a  sample  in 
two,  and  put  one  half  in  bright  sunlight,  while  the  other  half 
is  kept  in  a  book  away  from  the  light.  After  a  few  days  com- 
pare the  color.  It  is  easier  to  get  quick  results  with  this  test 
if  you  will  take  a  small  sample  of  the  dye  itself,  dissolve  it  in 
water,  and  smear  a  little  on  paper.  The  color  smear  should 
be  dark  at  one  end,  and  very  light  at  the  other.  Cut  in  two 
as  before  and  expose  to  light.  As  one  end  of  the  smear  is  so 
light,  it  will  show  a  change  of  shade  much  sooner  than  will 
a  dyed  cloth  containing  a  considerable  amount  of  the  dye. 

Your  chemical  experience  will  suggest  to  you  similar  ways 
in  which  you  can  test  any  dyed  material  for  any  desired 
quality  of  fastness.  Many  of  the  artificial  dyes  are  of  exceed- 
ingly good  quality  in  every  way,  and  it  is  possible  to  find  a 
dye  that  will  give  almost  any  color  on  any  material  and  that 
will  be  fast  enough  for  any  practical  end. 


DYES  AND   DYEING  349 

Natural  dyes.  Formerly  all  dyeing  was  done  with  the  aid 
of  indigo,  logwood,  cochineal,  etc.  Most  of  these  have  been 
superseded'by  artificial  dyes.  Logwood,  however,  still  holds 
its  own  in  wool  dyeing.  Many  of  these  colors  are  dyed  by 
the  aid  of  mordants,  and  our  next  study  will  be  to  see  just 
how  a  dye  that  has  no  natural  affinity  for  a  fiber  can  be  made 
to  stick  to  it. 

Lakes.  The  addition  of  ammonia  to  a  solution  of  an  alu- 
minium salt  yields  a  white  gelatinous  precipitate  of  aluminium 
hydroxide.  This  has  an  affinity  for  dyes,  so  that  if  a  solu- 
tion of  litmus  is  shaken  with  the  precipitate  the  color  and  the 
aluminium  hydroxide  form  a  loose  chemical  combination 
called  a  lake.  The  lakes  used  in  painting,  such  as  carmine 
lake  and  rose  lake,  are  made  in  this  way.  These  lakes  may 
have  iron,  tin,  chromium,  or  other  metals  substituted  for  the 
aluminium. 

Aluminium  as  a  mordant.  Cotton  has  no  affinity  for  log- 
wood dye.  If  we  soak  cotton  in  a  logwood  solution,  it  will  be 
stained,  but  on  washing,  the  stain  will  almost  entirely  dis- 
appear. 

The  color  is  not  fast.  Let  us,  however,  first  soak  the 
cotton  in  alum,  and  then  in  ammonia.  This  will  precipitate 
aluminium  hydroxide  on  the  fiber.  If  the  cotton  is  now 
soaked  in  logwood,  the  color  will  be  absorbed,  not  by  the 
cotton  but  by  the  aluminium  hydroxide,  forming  a  lake. 
The  color  will  then  be  fast.  Materials  used  in  this  way  to 
fasten  colors  on  fabrics  are  called  mordants,  and  the  dyes  are 
known  as  mordant  dyes.  Salts  of  tin  and  iron  and  chromium 
are  largely  used,  as  well  as  tannic  acid. 

Logwood  is  one  of  the  mordant  dyes.  It  gives  a  good 
cheap  black,  and  is  used  extensively  on  wool  and  silk.  By 
using  tin  as  the  mordant,  silk  may  be  weighted  so  that  the  silk 


350  CHEMISTRY   IN  THE  HOME 

will  weight  400  times  as  much  as  the  raw  material.  Such 
weighting  as  this,  however,  is  objectionable,  as  the  silk  will 
crack  and  wear  poorly. 

Indigo.  Indigo  blue,  or  indigotin,  as  the  color  is  called,  was 
formerly  obtained  from  the  indigo  plant.  It  is  now  made 
synthetically  in  large  amounts  and  the  natural  product  is  dis- 
appearing from  the  market.  The  color  is  insoluble  in  water, 
but  when  reduced  becomes  soluble,  in  which  form  it  is  colorless. 
Before  dyeing,  the  indigo  is  reduced  with  acid  sodium  sulphite, 
NaHSOs.  This  makes  the  indigo  both  soluble  and  colorless. 
The  cloth  is  then  entered  and  the  dye  made  to  soak  into  the 
fibers.  The  cloth  is  then  removed  and  exposed  to  the  air. 
The  indigo  reoxidizes  and  the  indigo  blue  develops.  It  is 
an  exceedingly  fast  color,  and  is  extensively  used  for  blue 
serges. 

Artificial  dyes.  The  artificial  dyes  come  under  many  chem- 
ical classes,  and  we  can  consider  only  a  few  of  them.  The 
ones  given  below  constitute  some  of  the  more  important, 
and  will  illustrate  the  subject. 

Acid  dyes.  The  commercial  dyestuff  is  usually  an  alkali 
or  calcium  salt  of  the  color  acid.  When  used  with  wool,  the 
wool  acts  as  a  base,  setting  free  and  combining  with  the  color 
acid,  and  forming  an  insoluble  compound.  Alkalies  will 
render  the  color  soluble  and  remove  it,  hence  fibers  dyed  with 
these  colors  should  not  be  washed  with  washing  compounds 
containing  alkalies.  They  are  generally  fast  to  light,  and 
hence  are  useful  in  dyeing  such  things  as  feathers  that  do  not 
require  washing.  Seventy-five  per  cent  of  the  wool  is  dyed 
with  these  dyes  in  an  acid  bath.  Acid  dyes  are  also  used 
with  silk,  but  not  for  cotton.  They  are  important  in  the 
dyeing  of  jute.  The  process  of  dyeing  on  wool  is  simple. 
The  dye,  together  with  15  per  cent  Glauber's  salt  and  3  per 


DYES  AND   DYEING  351 

cent  of  sulphuric  acid,  based  on  the  weight  of  the  material 
that  is  to  be  dyed,  is  placed  in  water  heated  to  140°  F.  when 
the  goods  are  entered.  The  bath  is  then  heated  to  boiling 
and  the  boiling  continued  for  about  three  quarters  of  an  hour. 
They  are  then  removed  and  rinsed. 

Basic  colors.  These  colors  are  characterized  by  their 
bright  or  even  gaudy  colors.  They  are  not  very  fast  to 
light,  but  are  to  washing.  They  are  basic  in  character,  hence 
the  name.  They  have  an  affinity  for  wool  and  silk,  but  not 
for  cotton.  They  are  used  largely  for  silk.  If  we  wish  to  use 
them  with  cotton,  we  must  first  mordant  the  fiber,  using 
tannic  acid. 

Direct  or  substantive  colors.  The  name  direct  is  given  to 
this  class  because  they  will  dye  directly  on  cotton.  All 
vegetable  fibers  absorb  them,  as  do  the  animal  fibers,  but  for 
them  the  acid  colors  are  preferable.  The  direct  colors  are 
used  extensively  in  union  goods,  that  is,  mixtures  of  cotton  and 
wool,  and  cotton  and  silk,  as  the  dye  will  color  both  fibers. 
Glauber's  salt  is  usually  added  to  the  bath  to  diminish  the 
solubility  of  the  dye  and  aid  its  deposition  on  the  fiber.  A 
concentrated  bath  is  better  than  a  dilute  one.  A  treatment 
with  a  solution  of  copper  sulphate  after  dyeing  improves  the 
fastness  of  the  color.  They  vary  much  in  fastness,  being 
generally  not  fast  to  washing  on  cottons  and  faster  on  wools. 

Bleeding.  Many  dyes,  and  the  direct  dyes  on  cotton  in 
particular,  are  subject  to  a  trouble  called  bleeding.  If  you 
will  take  a  skein  of  cotton  dyed  with  rhodamine  or  some  other 
direct  dye,  twist  it  with  a  white  skein,  and  then  boil  the  two 
in  water,  you  will  find  that  at  the  end  of  an  hour  both  skeins 
will  be  colored.  The  color  has  bled  from  one  to  the  other. 
This  aids  level  dyeing,  but  causes  the  color  to  run  in 
washing. 


352  CHEMISTRY   IN   THE   HOME 

Sulphur  colors.  These  are  known  as  sulphur  colors,  both 
because  they  contain  sulphur  and  because  sodium  sulphide 
is  used  in  the  dye  bath.  They  are  fast  to  light,  to  acids,  and 
to  washing.  They  are  only  suitable  for  vegetable  fibers,  as 
the  strong  alkali  used  in  the  dye  bath  attacks  the  animal 
fibers.  The  colors  are  generally  dull.  A  sample  dye  bath 
would  be  :  dye  1-20  per  cent  of  the  weight  of  the  material  to 
be  dyed ;  sodium  sulphide  1-4  times  the  weight  of  the  dye- 
stuff;  Glauber's  salt  20-50  per  cent;  and  soda  ash  5-10  per 
cent  of  the  weight  of  the  material.  Enter  goods  just  below 
the  boiling  point,  and  boil  for  one  hour.  The  colors  are  all 
insoluble  in  water,  but  are  soluble  in  sodium  sulphide. 

Alizarin  colors.  The  alizarin  or  artificial  mordant  colors 
are  always  used  with  mordants,  usually  chromium,  alu- 
minium, or  iron.  They  are  very  fast  to  both  light  and  wash- 
ing. Alizarin  is  the  most  important  dye  of  the  group. 

Miscellaneous  colors.  There  are  many  other  classes  of 
colors,  and  many  that  do  not  fall  into  any  special  class.  One 
of  the  most  important  of  these  is  aniline  black,  produced 
by  the  oxidation  of  aniline  hydrochlorate.  There  may  be  in 
your  home  a  table  that  you  would  like  to  use  for  a  home  lab- 
oratory bench.  To  be  suitable  for  this  use  it  should  be 
finished  in  such  a  way  that  chemicals  will  not  readily  act  on  it, 
and  that  it  looks  well,  and  is  easily  kept  in  condition.  You 
may  gain  all  these  ends  by  staining  it  with  aniline  black. 

First  see  that  the  wood  is  clean,  and  that  no  trace  of  a 
former  finish  is  left.  Then  apply  two  coats  of  a  solution 
composed  of  5  ounces  of  copper  sulphate,  and  5  ounces  of 
potassium  chlorate,  dissolved  in  2|  pints  of  water.  This 
solution  should  be  applied  hot,  the  second  coat  to  follow  as 
soon  as  the  first  is  dry.  When  these  are  dry,  apply  a  solution 
consisting  of  6  ounces  of  aniline  chloride  crystals  dissolved 


DYES  AND   DYEING  353 

in  2\  pints  of  water.  This  solution  should  also  be  applied  hot. 
When  all  is  dry,  rub  in  thoroughly  raw  linseed  oil,  using  a 
cloth  so  as  to  secure  a  thin  coating.  Rub  thoroughly  and 
hard  in  order  to  bring  out  a  good  polish.  Finally,  wash  with 
hot  soapsuds.  This  is  the  formula  used  in  many  high  schools 
to  finish  the  laboratory  table  tops  black. 

SUMMARY 

Material  to  be  dyed  must  be  clean,  must  be  stirred  while  in  the  dye 
bath,  and  dyed  hot. 

Indigo,  logwood,  and  cochineal  are  natural  dyes. 

A  lake  is  the  combination  of  a  metallic  hydroxide  with  a  color. 

A  mordant  is  a  substance  used  to  make  a  color  stick  to  a  fiber  for 
which  it  has  no  affinity. 

Acid  dyes  are  chiefly  used  for  wool.  Commercially  they  are  the 
alkali  or  calcium  salt  of  the  color  acid.  Examples:  acid  ma- 
genta, patent  blue,  scarlet  2  R. 

Basic  dyes  are  used  mainly  for  mordanted  cotton.  Examples  : 
rhodamine,  phosphine,  magenta,  bismarck  brown. 

Direct  dyes  are  largely  used  in  dyeing  cotton  and  union  goods. 
Examples:  primulin,  benzo  orange  R,  Congo  red  4  R. 

Alizarin  dyes.     Very  fast.     Alizarin  the  most  important. 

Aniline  black  is  made  by  the  oxidation  of  aniline  hydrochlorate. 

Colors  are  tested  for  fastness  by  exposure  to  light,  acid,  or  what- 
ever special  quality  is  desired. 

Exercises 

1.  How  would  you  dye  an  ostrich  plume  yellow?     What  class 
of  dyes  would  be  suitable  ? 

2.  A  home-dyed  dress  showed  after  pressing  large  rings   of  a 
lighter  color.     What  was  one  possible  source  of  the  trouble? 

3.  Could  you  make  a  red  ink  from  a  red  dye?     How? 

4.  What  dyes  would  you  use  to  dye  raffia  a  bright  red?    Would 
the  color  be  fast  to  light  ? 

6.   Why  cannot  a  gray  be  dyed  "over  a  green  ? 
6.   There  are  many  more  shades  of  colored  goods  than  there  are 
dyes.     How  are  they  produced? 


CHAPTER  XXXI 
SOME   COMMON   CHEMICALS 


FIG.  121.  —  Making  artificial  rubies. 
The  aluminium  oxide  is  carried  from 
B  a  little  at  a  time  through  C.  In 
passing  through  the  oxyhydrogen 
flame  it  is  fused  and  forms  the  boule 
F ;  J-M  show  supports  with  boules 
in  various  stages  of  completion. 

354 


Reference  books  needed. 
In  an  elementary  chemistry 
it  is  impossible  to  consider 
all,  or  even  a  majority  of, 
the  common  chemicals.  All 
that  such  a  chemistry  as  this 
can  do  is  to  start  you  on  the 
road  of  chemical  knowledge, 
and  teach  you  how  and 
where  to  look  for  additional 
information.  When  you 
wish  to  know  about  some 
chemical  that  is  not  studied 
in  this  chemistry,  go  to  your 
library.  The  librarian  will 
show  you  how  to  use  the 
card  index,  and  after  a 
little  practice  you  will  see 
how  easy  and  helpful  the 
use  of  reference  books  is. 

Some  chemicals,  however, 
that  we  have  not  studied 
are  so  important,  that,  al- 
though we  cannot  spare  the 
time  to  study  them  in  de- 
tail, a  few  facts  about  them 
should  be  known. 


SOME   COMMON   CHEMICALS 


355 


Aluminium  oxide.  Aluminium  oxide,  A12O3,  occurs  in 
nature  as  the  mineral  corundum.  This,  when  pure,  forms 
transparent,  hard  crystals,  that  when  cut  are  a  good  substi- 
tute for  the  diamond.  When  colored  by  the  addition  of  small 
quantities  of  impurities,  corundum  forms  the  ruby  and  the 
sapphire.  By  melting  aluminium  oxide,  mixed  with  small 
quantities  of  metallic  oxides,  it  is  possible  to  produce  syn- 
thetic rubies  and  sapphires  that  are  the  equals  of  the  natural 
in  beauty  (Fig.  121). 


Carborundum  furnace. 


Much  of  the  natural  aluminium  oxide  occurs  mixed  with 
iron  oxide  in  a  black  rock  called  emery.  This  is  used  as  an 
abrasive.  Aluminium  oxide  can  be  fused  in  the  electric 
furnace,  when  it  forms  an  exceedingly  hard  mass,  that  when 
broken  up  is  called  alundum.  This  is  broken  to  a  powder  and 
used  as  an  abrasive. 

Abrasives.  An  abrasive  is  a  material  used  in  grinding  and 
polishing  hard  substances.  Sandstone  and  emery  are  two 
natural  abrasives.  Alundum  is  an  artificial  abrasive.  By 
heating  sand  and  coke  in  an  electric  furnace  carbide  of  silicon 
is  formed. 

WEED    CHEMISTRY 23 


356 


CHEMISTRY   IN   THE   HOME 


SiO2  +  3  C  ->  SiC  +  2  CO 

This  silicon  carbide 
is  called  carborundum 
and  forms  beautiful 
crystals,  iridescent  on 
the  surface.  It  is  so 
hard  that  it  is  widely 
used  as  an  abrasive, 
many  different  kinds 
of  polishing  and  grind- 
ing wheels,  powders, 
and  stones  being  made 
from  it. 

Thermit.  A  mix- 
ture of  powdered  aluminium  and  iron  oxide,  called  thermit, 
burns  with  the  production  of  an  intense  heat.  At  the  same 
time  the  iron  oxide  is  reduced  to  metallic  iron  and  melts. 


FIG.  123.  —  Thermit  welding.     Preparing 
molds  about  rail  joints. 


2  Al  +  Fe2O3 
By  igniting  thermit 
in  a  crucible  having 
a  hole  in  the  bottom 
that  can  be  closed, 
placing  the  crucible 
over  a  broken  iron 
article  that  is  to  be 
repaired,  and  then 
allowing  the  fused 
iron  produced  to  flow 
out  upon  the  break, 
the  two  pieces  of  iron 
can  be  welded  to- 


2  Fe  +  A1203 


FIG.    124.  —  Thermit   welding.      Thermit   in 
crucibles  over  the  molds. 


SOME   COMMON   CHEMICALS 


357 


gether.  In  this  way  large  broken  articles  can  be  easily 
and  cheaply  repaired. 

By  mixing  aluminium  with  the  oxides  of  other  metals,  as 
chromium,  and  ignit- 
ing, the  metallic  ox- 
ide can  be  reduced 
and  the  pure  metal 
obtained.  This  is  a 
satisfactory  method 
of  obtaining  such 
metals  as  manganese 
and  chromium. 

Alums.  The  sul- 
phate of  aluminium 
forms  loose  chemical 
compounds  with 
many  other  sul- 
phates. These 
double  milnhafps  are  FlG-  125.  — Nitrogen  cycle.  (From  Blanchard 

and  Wade's  Foundations  of  Chemistry.} 

known      as      alums. 

Potassium  alum,  K2SO4  •  A12(SO4)3  •  24  H2O,  sodium  alum, 
and  chrome  alum  are  common  alums.  They  are  used  in 
dyeing,  in  water  purification,  and  in  baking  powders. 

Nitric  acid  and  nitrates.  Nitric  acid  is  prepared  by  the 
action  of  sulphuric  acid  upon  a  nitrate.  Sodium  or  potas- 
sium nitrate  is  commonly  used.  The  mixture  is  heated  in 
a  retort,  when  the  nitric  acid  distills  .over. 

NaN03  +  H2SO4  ->  NaHSO4  +  HNO3 

Nitric  acid  is  a  colorless,  heavy  liquid  having  a  sweetish 
smell,  and  is  very  corrosive.  It  is  a  strong  oxidizing  agent. 
Recently  large  quantities  have  been  made  by  blowing  air 


358  CHEMISTRY  IN   THE  HOME 

through  electric  arcs.  The  intense  heat  of  the  arc  causes  the 
nitrogen  and  oxygen  of  the  air  to  combine,  forming  oxide  of 
nitrogen.  This,  when  dissolved  in  water,  forms  nitric  acid. 
The  process  is  important  because  this  synthetic  acid  is  used 
to  prepare  the  nitrates  that  are  indispensable  in  fertilizers. 

This  process  is  another  illustration  of  the  usefulness  of 
chemistry  to  industry.  Fertilizers  must  contain  nitrogen  in 
such  a  form  that  plants  can  assimilate  it.  The  substance 
commonly  used  has  been  sodium  nitrate.  The  supply  of 
this  Chili  saltpeter  (so  called  because  it  comes  from  Chili)  is 
almost  exhausted,  and  if  it  were  not  possible  for  the  chemist 
to  make  synthetic  nitric  acid,  the  shortage  of  nitrates  would 
soon  cause  very  serious  trouble  to  the  farmer. 

A  mixture  of  nitric  and  sulphuric  acids  when  run  into 
glycerin  changes  it  to  a  nitrate.  This  is  nitroglycerin,  the 
violent  explosive. 

C3H5(OH)3  +  3  HNQg  +  (H2SO4)  -^  C8H6(NCW,  + 

3  H2O  +  (H2SO4) 

Absorbing  this  in  ground  wood,  or  some  other  porous 
material,  gives  dynamite.  Some  oxidizing  material,  as  a 
nitrate,  is  also  usually  added.  Most  of  the  other  high 
explosives  owe  their  power  to  their  being  nitrates.  Gun- 
cotton  is  cellulose  hexanitrate  [C^HnO^NOs^L,  prepared 
by  treating  cotton  with  a  mixture  of  nitric  and  sulphuric 
acids.  In  making  nitroglycerin  and  guncotton  the  sul- 
phuric acid  takes  no  part  in  the  chemical  change,  but  is 
used  as  a  dehydrating  agent.  A  lower  cellulose  nitrate  is 
used  in  preparing  collodion. 

Phosphorus.  When  a  mixture  of  calcium  phosphate,  sand, 
and  carbon  is  heated  in  an  electric  furnace,  the  phosphate 
is  reduced  by  the  carbon  and  the  element  phosphorus  ob- 


SOME   COMMON   CHEMICALS  359 

tained.  The  temperature  of  the  furnace  is  so  high  that  the 
phosphorus  is  volatilized  and  escapes  as  a  vapor  which  is 
led  into  water  and  there  condensed. 

Phosphorus  is  a  pale  yellow,  brittle  solid.  It  melts 
at  111°  F.,  and  is  soluble  in  carbon  disulphide.  It  oxidizes 
so  readily  that  it  must  be  kept  under  water,  as  it  catches  fire 
in  the  air.  It  is  poisonous,  and  the  constant  inhaling  of 
even  small  quantities  of  its  vapor  causes  rotting  of  the  bones, 
and  eventually  death.  It  is  for  this  reason  that  its  use  in  the 
manufacture  of  matches  has  been  prohibited  in  many  coun- 
tries. 

When  yellow  phosphorus  is  heated  to  527°  F.,  out  of  con- 
tact with  the  air,  it  changes  to  a  dark  red  allotropic  modifi- 
cation. This  red  phosphorus  is  a  powder,  does  not  readily 
oxidize,  is  insoluble  in  carbon  disulphide,  is  nonvolatile,  and 
is  not  poisonous.  By  heating  it  to  a  still  higher  temperature 
than  that  required  to  form  it,  it  is  converted  into  the  usual 
yellow  form.  The  main  use  of  phosphorus  is  in  the  manu- 
facture of  matches. 

Matches.  The  head  of  the  ordinary  parlor  or  friction 
match  is  composed  of  a  mixture  of  yellow  phosphorus,  an 
oxidizing  agent,  an  abrasive  as  powdered  glass,  and  glue 
to  hold  the  mass  together.  A  coloring  material  is  often 
added,  and  sometimes  sugar  to  aid  the  combustion.  The  top 
of  the  wooden  splint  is  sometimes  dipped  in  paraffin  to  make 
it  inflame  more  readily.  These  matches  ignite  when  rubbed 
on  a  rough  surface  because  the  heat  of  friction  heats  the 
phosphorus  to  its  kindling  temperature.  The  oxidizing 
agent  present  aids  the  combustion,  which  soon  heats  the  wood 
of  the  match  stick  to  its  burning  point. 

These  matches  are  dangerous;  for  if  dropped  on  the  floor 
and  stepped  on,  they  may  start  a  fire.  Children,  too,  some- 


360  CHEMISTRY   IN   THE   HOME 

times  suck  the  heads  of  the  matches  and  die  from  phosphorus 
poisoning.  An  improvement  is  to  substitute  for  phosphorus 
the  less  poisonous  compound,  phosphorus  sesquisulphide. 

Safety  matches  have  the  head  composition  divided  into 
two  parts.  Red  phosphorus,  powdered  glass,  and  glue  are 
on  the  outside  of  the  match  box,  while  the  composition  on 
the  head  of  the  wooden  splint  contains  the  oxidizing  agent, 
an  abrasive,  and  glue.  When  these  matches  are  rubbed  on 
the  box,  the  heat  developed  converts  a  minute  portion  of  the 
red  phosphorus  to  yellow,  it  burns,  and  the  match  catches 
fire.  Their  great  advantage  is  that  they  cannot  be  ignited 
except  on  the  box.  This  is  not  quite  true ;  for  if  you  will 
carefully  rub  a  safety  match  on  glass,  it  is  possible  to  heat 
the  head  composition  to  its  kindling  point,  and  the  match 
will  burn.  Under  ordinary  conditions,  however,  the  composi- 
tion will  wear  off  by  friction  before  it  catches  on  fire.  The 
wood  of  the  match  splint  is  usually  soaked  in  some  chemical 
that  prevents  the  spark  from  glowing  after  the  match  is 
extinguished. 

Sulphur.  Large  deposits  of  sulphur  occur  in  Mexico, 
Sicily,  and  Louisiana,  as  well  as  in  many  other  parts  of  the 
earth.  The  Louisiana  sulphur,  which  is  the  source  of  prac- 
tically all  of  the  sulphur  used  in  the  United  States,  occurs 
buried  many  hundred  feet  below  the  surface  of  the  ground. 
As  sulphur  is  cheap,  it  would  not  pay  to  sink  a  shaft  and  mine 
the  sulphur ;  instead  the  sulphur  is  melted  in  the  ground  and 
then  pumped  out. 

To  obtain  the  sulphur,  concentric  pipes  are  driven  down  to 
the  deposit.  Through  one  of  these  pipes  water  heated  to  a 
temperature  of  350°  F.,  under  a  pressure  of  100  pounds  to  the 
square  inch,  is  forced.  This  superheated  water  melts  the 
sulphur.  Through  the  second  pipe,  hot  compressed  air  is 


SOME   COMMON  CHEMICALS  361 

forced.  This  forces  the  melted  sulphur,  mixed  with  air  bub- 
bles, to  come  to  the  surface  through  the  third  pipe.  When 
it  reaches  the  surface,  it  is  allowed  to  flow  into  large  bins 
inclosed  in  rough  boards,  where  it  solidifies  into  masses  of 
as  much  as  100,000  tons.  The  sulphur  produced  is  over 
99  %  pure. 

Sulphur  is  a  yellow,  brittle  solid,  insoluble  in  water,  but 
readily  soluble  in  carbon  disulphide.  Heated  in  the  air  it 
first  melts  and  then  burns  to  sulphur  dioxide.  It  occurs  in 
several  allotropic  forms,  but  the  two  common  commercial 
forms  are  roll  sulphur  and  flowers  of  sulphur.  Roll  sulphur 
is  prepared  by  melting  sulphur  and  casting  it  in  wooden 
molds.  Flowers  of  sulphur  is  prepared  by  boiling  the  sulphur 
and  passing  the  vapor  into  large  brick  rooms,  where  it  con- 
denses to  a  fine  powder. 

Sulphur  is  used  in  enormous  quantities  in  the  manufacture 
of  sulphuric  acid,  in  making  sulphur  dioxide,  carbon  disul- 
phide, and  sulphur  dyestuffs,  in  vulcanizing  India  rubber, 
and  in  gunpowder. 

Sulphur  dioxide.  When  sulphur  is  burned,  sulphur  diox- 
ide, SO2,  is  formed.  This  is  a  colorless  gas,  easily  condensed 
to  a  liquid.  It  has  a  suffocating  odor  and  is  a  good  bleaching 
and  reducing  agent.  By  dissolving  it  in  water  sulphurous 
acid  is  formed. 

H2O  +  SO2  ->  H2SO3 

The  salts  of  sulphurous  acid,  called  sulphites,  are  food  pre- 
servatives. Sodium  sulphite,  Na2SO3,  is  a  crystalline,  white 
compound,  used  in  almost  every  photographic  developer. 
Sulphur  dioxide  is  a  reducing  agent  and  is  widely  used  as  a 
bleaching  and  disinfecting  agent. 

Sulphur  trioxide.  If  a  mixture  of  sulphur  dioxide  and  oxy- 
gen is  passed  over  finely  divided  platinum,  they  combine 


362  CHEMISTRY  IN   THE  HOME 

and  form  sulphur  trioxide,  SO3.  This  is  a  colorless  liquid  that 
solidifies  at  59°  F.  If  a  trace  of  water  vapor  is  present,  the 
sulphur  trioxide  solidifies  in  the  form  of  beautiful  silky 
needles.  It  must  be  kept  in  sealed  bottles,  as  it  absorbs 
water  from  the  air  and  changes  to  sulphuric  acid. 

After  the  reaction  the  platinum  remains  unchanged.  It 
has  served  a  similar  purpose  to  the  manganese  dioxide  used 
in  preparing  oxygen  ;  it  has  hastened  a  chemical  change,  but 
has  itself  undergone  no  permanent  change.  It  is  a  catalytic 
agent  or  a  catalyzer.  The  action  is  called  catalysis. 

Sulphuric  acid.  Sulphuric  acid  is  used  in  so  many  chem- 
ical processes  that  it  may  be  regarded  as  the  most  important 
acid.  It  is  prepared  in  two  ways,  first  by  the  contact  and 
second  by  the  chamber  process. 

In  the  contact  process  sulphur  or  pyrite  is  burned  to  fur- 
nish sulphur  dioxide.  This  is  mixed  with  air  and  passed  over 
iron  oxide,  which  is  kept  at  a  temperature  of  about  650°  F. 
The  iron  oxide  acts  as  a  catalytic  agent,  converting  the  sul- 
phur dioxide  to  trioxide.  This  is  dissolved  in  dilute  sul- 
phuric acid,  forming  the  acid  of  commerce. 

S  +  02  -*  S02 


H20->H2S04 

The  chemical  changes  involved  in  the  chamber  process  are 
very  complicated.  In  general,  the  change  of  sulphur  dioxide 
to  the  trioxide  is  carried  out  by  the  use  of  oxides  of  nitrogen 
as  catalytic  agents;  that  is,  their  alternate  oxidation  and 
reduction  carry  the  oxygen  to  the  sulphurous  acid,  changing 
it  to  sulphuric  acid. 

Sulphuric  acid  is  a  colorless,  heavy  liquid  having  a  specific 
gravity  of  1.84.  It  boils  at  640°  F.  Its  common  name  is  oil 


SOME   COMMON   CHEMICALS 


363 


of  vitriol,  for  it  was  formerly  made  by  distilling  green  vitriol, 
and  the  liquid  is  of  an  oily  appearance. 

The  action  of  dilute  sulphuric  acid  upon  metals  is  the  same 
as  that  of  other  acids.  In  hot  concentrated  solutions,  how- 
ever, it  acts  as  an  oxidizing  agent.  To  illustrate  :  if  copper  is 
heated  with  concentrated  sulphuric  acid,  hydrogen  is  first 


\fxit  Pipe 

/•  Strong  Ac/cffenA 


FIG.  126.  —  Chamber  process  for  the  manufacture  of  sulphuric  acid. 
(From  Thorp's  Outlines  of  Industrial  Chemistry.) 


set  free.  This  nascent  hydrogen  is  oxidized  by  the  hot  acid 
to  water.  The  sulphuric  acid  is  at  the  same  time  reduced 
to  sulphurous  acid,  which  at  the  high  temperature  of  the 
reaction  breaks  up  into  sulphur  dioxide  and  water. 


Cu 


+ 

H2S04 

-> 

CuS04  -f 

-H2 

H2S04  - 

f     H2 

-+ 

H2SO3  -f 

-H20 

H2S03 

-> 

H20  + 

SO, 

2  H2SO4 

+  Cu 

—> 

CuSO4  -\ 

-  2  H20  - 

hSO2 

We  have  seen  two  illustrations  of  another  use  for  sulphuric 
acid,  the  preparing  of  other  acids.  You  will  recall  that  you 
prepared  hydrochloric  acid  by  the  action  of  sulphuric  acid 
on  sodium  chloride,  and  nitric  acid  by  the  action  of  sulphuric 


364  CHEMISTRY   IN   THE  HOME 

acid  upon  a  nitrate.  A  similar  action  occurs  whenever 
sulphuric  acid  is  heated  with  the  salt  of  another  acid,  the 
boiling  point  of  which  is  lower  than  that  of  sulphuric  acid ; 
that  is,  the  acid  is  set  free. 

Another  important  use  of  sulphuric  acid  is  as  a  drying  or 
dehydrating  agent.  Gases  can  be  dried  by  bubbling  them 
through  the  strong  acid,  provided  of  course  no  chemical 
change  takes  place.  It  would  be  impossible  to  dry  ammonia 
in  this  way,  as  it  would  combine  with  the  acid.  Dishes 
containing  strong  sulphuric  acid  are  often  placed  in  cases 
containing  delicate  apparatus  to  keep  the  air  dry  and  thus  pre- 
vent the  corrosion  of  metal  parts. 

So  great  is  the  affinity  of  sulphuric  acid  for  water  that  it 
will  withdraw  hydrogen  and  oxygen  from  organic  materials, 
even  where  they  are  not  combined  in  the  form  of  water. 
A  sirup  of  sugar  mixed  with  strong  sulphuric  acid  will 
froth  up,  turn  black,  and  a  pasty  mass  of  carbon  will  be 
formed.  Wood,  flesh,  fabrics,  all  are  charred  in  the  same 
way.  This  makes  sulphuric  acid  dangerous;  for  if  dilute 
acid  is  spilled,  the  water  will  evaporate,  and  when  the 
acid  becomes  concentrated,  it  will  char  whatever  organic 
matter  it  is  in  contact  with. 

Sulphates.  As  sulphuric  acid  has  two  replaceable  hydrogen 
atoms,  it  can  form  two  sulphates,  a  normal  and  an  acid. 
Sodium,  for  example,  forms  sodium  acid  sulphate,  or  sodium 
bisulphate,  NaHSC>4,  as  well  as  the  normal  sodium  sulphate, 
Na2SC>4.  The  sulphates  were  formerly  called  vitriols,  and 
the  name  still  is  used  with  a  few  compounds.  Copper 
sulphate,  CuSCX,  is  blue  vitriol ;  ferrous  sulphate,  FeSCX,  green 
vitriol ;  and  zinc  sulphate,  ZnSC>4,  white  vitriol. 

Hydrogen  sulphide.  Hydrogen  sulphide,  also  called 
hydrosulphuric  acid,  H2S,  is  prepared  by  the  action  of  sul- 


SOME  COMMON   CHEMICALS  365 

phuric  acid  upon  a  sulphide.  Usually  ferrous  sulphide  is 
used. 

FeS  +  H2S04  -»  FeSO4  +  H2S 

It  is  a  colorless  gas,  about  three  volumes  dissolving  in 
one  of  water  at  ordinary  temperatures.  It  has  a  weak  taste, 
and  an  exceedingly  disagreeable  odor,  resembling  that  of 
rotten  eggs.  It  is  a  poison,  even  small  quantities  producing 
nausea  and  headache.  It  burns,  forming  sulphur  dioxide 
and  water.  Chemically  it  is  a  weak  acid,  forming  sulphides 
with  metals.  Its  main  use  is  as  a  reagent  in  the  chemical 
laboratory. 

Sulphides.  The  oxidized  silver  of  the  jeweler  is  really 
silver  that  has  been  dipped  in  a  solution  of  potassium  sul- 
phide, and  thus  a  coat  of  silver  sulphide  formed  on  the  out- 
side. Many  copper  articles  are  finished  in  the  same  way. 
If  the  coating  is  polished,  it  forms  a  lustrous  black,  while 
if  it  is  burnished  off  in  spots,  so  that  the  metal  shows 
through,  a  mottled  appearance  results.  Sodium  and  po- 
tassium sulphides  are  used  in  photography  to  tone  bro- 
mide prints. 

Carbon  disulphide.  When  sulphur  vapor  is  passed  over 
red-hot  carbon  the  two  elements  combine,  forming  carbon 
disulphide.  The  operation  is  usually  carried  out  in  an 
electric  furnace.  In  this  case,  as  in  most  others,  the 
electricity  has  nothing  to  do  with  the  chemical  change, 
but  is  used  as  a  convenient  and  easily  controlled  method  of 
heating. 

Carbon  disulphide  is  a  heavy,  colorless  liquid,  boiling 
at  115°  F.  As  usually  found  in  commerce  it  has  a  nauseating 
odor,  but  when  pure  its  odor  is  pleasant  and  ethereal.  It  is 
very  inflammable.  It  is  extensively  used  as  an  insecticide, 
and  as  a  solvent  for  resins  and  gums. 


366  CHEMISTRY   IN   THE  HOME 

Zinc  white.  A  natural  mixture  of  the  oxides  of  iron  and 
zinc  called  franklinite  occurs  in  New  Jersey.  If  this  is 
heated  in  a  furnace  with  carbon,  the  zinc  is  reduced  and 
volatilized.  As  this  zinc  vapor  leaves  the  furnace  a  current 
of  air  is  blown  into  it,  when  the  zinc  burns  to  zinc  oxide. 
The  zinc  oxide,  ZnO,  called  zinc  white,  is  passed  into  can- 
vas bags,  where  the  waste  gases  are  filtered  out,  and  the  zinc 
white  collected.  It  is  used  as  a  pigment  in  white  paints  and 
as  a  filler  in  rubber  goods.  It  has  the  advantage  in  paints 
over  lead  white  that  sulphur  compounds  do  not  turn  it 
black. 

Lead  white.  Thin  perforated  discs  of  lead  are  placed  in 
small  earthenware  pots  about  ten  inches  high.  Dilute 
acetic  acid  is  then  poured  in  and  the  pots  packed  closely 
together,  the  space  between  them  and  over  them  being  filled 
with  tan  bark.  The  corroding  room  is  filled  in  this  way  with 
row  after  row  of  the  pots.  The  process  of  forming  the  lead 
white,  2  PbCO3  •  Pb(OH)2,  is  a  catalytic  one.  Basic  lead 
acetate  first  forms ;  this  is  decomposed  by  the  carbon  dioxide 
produced  by  the  fermenting  tan  bark,  and  basic  lead  car- 
bonate produced.  This  sets  free  the  acetic  acid,  which  in 
turn  forms  more  lead  acetate,  and  so  the  process  goes  on. 
The  process  requires  about  three  months  for  its  completion. 
There  are  quick  processes,  but  the  product  is  thought  to 
be  inferior.  White  lead  is  the  pigment  in  much  paint.  It 
is  apt  to  discolor  in  city  air,  as  the  hydrogen  sulphide  present 
converts  it  into  lead  sulphide,  PbS,  a  black  compound. 

The  halogens.  Fluorine,  chlorine,  bromine,  and  iodine 
form  the  halogen  or  chlorine  family.  Their  name  comes 
from  a  word  meaning  "  I  form  salts,"  which  is  given  to  them 
because  they  all  form  salts,  such  as  are  found  in  the  ocean. 
Their  properties  vary  in  a  periodic  manner,  which  follows 


SOME   COMMON  CHEMICALS 


367 


the  order  of  their  atomic  weights.     The  group  is  an  excellent 
illustration  of  what  is  meant  by  a  family  in  chemistry. 


NAME  OF 
ELEMENT 

ATOMIC 
WEIGHT 

PHYSICAL 

STATE 

MELTING 
POINT 

COLOR 

CHEMICAL 
ACTIVITY 

F 

19 

gas 

-223° 

pale  yellow 

very  very 

great 

Cl 

35.5 

gas  easily 

-  102° 

darker  yel- 

very great 

liquefied 

low  green 

Br 

79.9 

liquid 

7° 

dark  red 

great 

I 

126.9 

solid 

107° 

violet  black 

much  less 

active 

If  you  will  examine  the  above  table,  you  will  see  that  the 
properties  of  chlorine  are  not  the  same  as  those  of  bromine, 
but  that  there  is  a  periodic  variation  in  them. 

Chlorine  is  prepared  by  the  oxidation  of  hydrochloric 
acid.  Bromine  then  will  be  prepared  in  a  similar  way,  but 
more  easily ;  for  since  bromine  is  not  as  active  chemically  as 
chlorine,  its  compounds  will  not  be  as  stable. 

Bromine  is  a  dark  red  liquid,  soluble  in  water,  and  having 
even  a  worse  effect  on  the  mucous  membranes  than  chlorine. 
It  is  used  in  preparing  certain  dyes,  and  in  making  bromides 
used  in  medicine  and  in  photography. 

Iodine  is  a  violet  black  solid,  easily  volatile,  and  giving 
a  vapor  of  a  magnificent  violet  color.  It  is  freely  soluble 
in  alcohol,  giving  the  tincture  of  iodine  that  we  have  all  used. 
The  iodides  are  largely  used  in  photography. 

Fluorine  has  no  industrial  use.  The  fluorides  are  of  value 
as  a  source  of  hydrofluoric  acid,  used  in  etching  glass,  and 
calcium  fluoride  is  used  as  a  flux  in  metallurgy. 

Periodic  law.     If  the  elements  are  arranged  in  the  order 


368  CHEMISTRY   IN  THE  HOME 

of  their  atomic  weights,  beginning  with  lithium,  a  singular 
fact  becomes  evident. 

Li        Be         B          C          N          O          F         Na       Mg 
7         9.1         11          12         14         16         19         23        24.4 

We  find  that  the  element  lithium  is  a  metal.  Beryllium  is 
a  metal,  but  is  less  metallic  than  lithium ;  boron  is  still  less 
metallic,  while  in  carbon  the  metallic  properties  are  quite 
lost.  As  we  go  on,  the  elements  become  more  nonmetallic 
until  fluorine  is  a  decided  nonmetal.  With  sodium,  however, 
the  pendulum  once  more  swings  back,  and  we  have  an  exceed- 
ingly metallic  element.  If  starting  with  sodium  we  place 
it  under  lithium  and  go  on  as  before,  we  find  that  chlorine 
comes  under  fluorine,  and  then  we  once  more  swing  back  to 
a  metal,  potassium. 

The  vertical  rows  thus  obtained  give  us  the  chemical 
families.  The  cause  of  this  is  not  yet  known,  and  the  table 
shows  some  inconsistencies,  yet  it  has  proved  of  much  use 
to  chemists.  The  above  is  the  barest  outline  of  the  facts, 
but  it  will  give  you  a  foundation  that  you  can  build  upon 
by  consulting  a  larger  work. 

To  know  the  members  of  the  chemical  families  in  the 
order  of  their  atomic  weights  is  useful  because  it  helps  us 
to  remember  their  properties.  To  illustrate  :  if  I  know  that 
sodium  and  potassium  are  both  members  of  the  same  family 
and  follow  each  other  in  that  order,  I  then  know  that  potas- 
sium will  be  more  active  than  sodium,  that  potassium  hydrox- 
ide will  be  a  stronger  base  than  sodium  hydroxide,  etc. 
Note  that  the  properties  of  the  members  of  a  family  are  not 
the  same,  but  that  they  show  a  regular  gradation  as  we  go 
from  element  to  element  in  the  same  family,  and  that  this 
applies  to  both  physical  and  chemical  properties.  It  is 


*O  i*""* 


s§ 


CO 

(N 


II 


II 

sg 
14 


o  M 


I! 
II 


<! 


03 

si 

II 


38 


H        > 

CO  QO 


l 


370  CHEMISTRY   IN  THE   HOME 

difficult  to  give  credit  to  the  author  of  such  a  generalization 
as  this,  for  many  men  have  worked  on  it,  each  improving 
the  idea  a  little.  The  Russian  chemist,  Mendeleeff,  was, 
however,  the  first  who  published  such  a  table  (1869). 

Milk  an  important  food.  The  fact  that  infants  thrive  on 
an  exclusive  diet  of  milk  shows  that  it  must  contain  all  of  the 
elements  needed  by  the  body ;  that  is,  that  it  must  be  a  com- 
plete food.  It  is  so  largely  used  by  young  children,  and  is 
so  easily  contaminated  with  germs,  and  so  difficult  to  keep, 
that  great  care  should  be  used  in  selecting  your  milkman. 

Many  cities  have  adopted  rigid  rules  for  the  regulation  of 
the  sale  of  milk,  for  it  has  been  conclusively  shown  that 
children's  diseases  and  the  sale  of  poor  milk  go  hand  in  hand. 
In  New  York  there  are  three  grades,  A,  B,  and  C,  sold.  Your 
milkman  can  tell  you  the  local  regulations,  and  usually  they 
are  printed  by  the  Board  of  Health  for  free  distribution. 
Read  them  and  see  if  you  know  the  reason  for  the  various 
restrictions  imposed  on  the  dealers. 

Composition  of  milk.  In  various  parts  of  the  world  the 
milk  of  goats,  mares,  and  reindeer  is  used,  but  to  us  milk 
always  means  cow's  milk.  Its  average  composition  is  water 
87.17,  sugar  4.88,  fat  3.69,  protein  3.55,  and  mineral  matter 
0.71.  The  composition  varies  within  wide  limits,  depending 
on  the  time  of  year  and  the  breed  of  the  cow,  as  well  as  on  the 
individual  cow  from  which  the  milk  is  drawn.  In  general 
the  laws  will  not  allow  a  milk  to  be  sold  that  contains  less 
than  3  %  of  butter  fat,  and  11.5%  of  total  solids.  Some 
cows  have  given  over  20,000  pounds  of  milk  a  year,  but  the 
average  is  less  than  one  fourth  of  this. 

Preserving.  Milk  is  an  ideal  culture  medium  for  bacteria. 
To  preserve  it,  it  must  be  carefully  protected  from  every 
source  of  contamination,  and  kept  cold.  The  addition  of 


SOME   COMMON   CHEMICALS  371 

preservatives,  as  formaldehyde  and  boric  acid,  is  very  objec- 
tionable and  is  prohibited  by  law. 

Pasteurized  milk.  To  sterilize  milk  it  must  be  heated  to 
the  boiling  point,  allowed  to  stand  and  then  heated  again  to 
the  boiling  point.  This  cooks  the  milk,  and  so  alters  its 
taste  that  the  process  is  impracticable.  If,  however,  the  milk 
is  heated  to  167°  F.,  for  20  minutes,  and  then  rapidly  cooled, 
the  taste  is  not  perceptibly  altered,  and  the  lactic  acid  bacteria 
are  killed.  The  milk  will  then  keep  sweet  for  several  days, 
if  it  is  kept  cold.  Pasteurized  milk  is  not  sterile,  and  the 
putrefactive  bacteria  present  will  multiply,  even  though  the 
milk  does  not  turn  sour. 

Condensed  milk.  Much  of  the  milk  produced  is  turned 
into  condensed  milk.  The  milk  is  placed  in  vacuum  pans, 
and  water  evaporated  until  a  thin  liquid  containing  about 
28  %  of  milk  solids  remains.  This  is  canned,  heated  again 
to  sterilize  it,  when  it  keeps  for  a  long  time.  Sugar  is  often 
added,  when  the  sugar  will  prevent  fermentation. 

Milk  powders.  Many  attempts  have  been  made  to  evapo- 
rate milk  and  sell  it  in  the  form  of  a  powder.  These  all  failed 
for  a  time  owing  to  the  difficulty  of  evaporating  such  a  mix- 
ture to  dryness,  and  reproducing  the  taste  of  raw  milk  in 
the  redissolved  powder.  Recently  the  problem  has  been 
solved  by  blowing  milk  through  fine  holes,  so  as  to  produce  a 
very  fine  spray,  into  a  hot  room.  The  hot  air  evaporates  the 
water  from  each  tiny  drop,  and  the  milk  powder  remains. 
It  is  freely  soluble  in  water,  and  gives  a  product  that  while 
not  identical  with  the  raw  milk,  is  close  to  it,  and  is  perfectly 
satisfactory  for  cooking.  The  powder  keeps  better  if 
skimmed  milk  is  used,  as  the  butter  fat  causes  the  product  to 
become  rancid.  Its  usefulness  in  camping,  or  to  sailors,  etc., 
is  evident. 

WEED    CHEMISTRY 24 


372  CHEMISTRY   IN  THE   HOME 

Homogenized  milk  is  milk  that  has  been  forced  through 
holes  much  smaller  than  the  average  diameter  of  the  fat  glob- 
ules present  in  milk.  A  pressure  of  about  2500  pounds  to  the 
square  inch  is  necessary  to  do  this.  The  result  is  that  the 
fat  globules  are  made  much  smaller,  and  a  more  perfect  emul- 
sion obtained,  that  does  not  separate  as  does  milk.  That  is, 
the  cream  does  not  readily  rise.  The  milk  is  much  thickened 
by  the  process.  The  homogenized  milk  is  largely  used  in  the 
manufacture  of  ice  cream. 

Butter.  Cream  that  has  ripened,  i.e.  slightly  soured,  when 
churned  gives  butter.  The  churning  process  brings  the  fat 
globules  together,  leaving  the  other  constituents  of  the  milk 
in  the  buttermilk,  which  has  about  the  same  composition  as 
skimmed  milk.  The  butter  is  worked  to  free  it  from  water, 
salted,  packed,  and  sold. 

Cheese.  Rennet,  which  is  an  extract  from  the  fourth 
stomach  of  the  calf,  obtained  by  soaking  the  stomach  in  a 
dilute  salt  solution,  has  the  power,  owing  to  a  ferment  that  it 
contains,  of  causing  the  casein  of  milk  to  turn  solid.  Junket 
tablets  contain  rennet,  and  cause  this  change.  This  is  the 
first  step  in  the  making  of  cheese. 

Rennet  is  added  to  milk,  and  after  the  mass  has  set  and  the 
curd  has  become  firm,  it  is  cut  into  cubes  and  allowed  to  stand. 
The  curd  shrinks,  becomes  harder,  and  the  whey  separates. 
The  curd  is  then  piled,  when  it  forms  a  solid  mass,  more  whey 
draining  from  it.  It  is  then  ground,  salted,  molded,  stored 
until  the  ripening  process  develops  a  satisfactory  flavor,  and 
marketed. 

The  countless  varieties  are  due  to  a  slight  extent  to  the  dif- 
ferent milks  used,  but  mainly  to  the  ripening  process,  dif- 
ferent molds  and  bacteria  giving  different  flavors. 

Fermented  milk.     Milk  that  has  soured  has  an  acid  taste, 


SOME   COMMON   CHEMICALS  373 

agreeable  to  many.  Buttermilk,  which  is  sour  skimmed 
milk,  has  a  large  sale.  Kumiss,  Fermalac,  and  Zoolak  are 
artificially  soured  milks.  They  are  said  to  be  easily  diges- 
tible. 

Oxalic  acid.  Potassium  and  calcium  oxalates  are  found 
in  plants,  as  the  rhubarb  and  sorrel.  The  acid  is  prepared 
by  heating  a  thick  paste  of  sawdust  and  sodium  hydroxide 
on  iron  plates.  Sodium  oxalate  is  formed,  from  which  the 
acid  is  extracted. 

Oxalic  acid,  H^O^  crystallizes  with  two  molecules  of 
water.  It  is  a  poison.  As  it  freely  dissolves  the  oxides  of 
metals,  it  is  much  used  in  the  home  in  metal  polishes  for 
brass  and  copper. 

Tartaric  acid.  Many  plants  contain  the  acid,  H2C4H4O6, 
tartaric  acid.  Commercially  it  is  obtained  from  the  impure 
potassium  hydrogen  tartrate  (argols)  that  separates  during 
the  fermentation  of  wine.  The  acid  is  used  in  dyeing,  and 
some  of  its  salts  are  important.  Seidlitz  powders  contain 
potassium  acid  tartrate  in  one  paper,  and  sodium  acid  car- 
bonate in  the  other.  On  mixing,  Rochelle  salt,  carbon 
dioxide,  and  water  are  formed.  With  the  use  of  tartrates 
in  baking  powders  we  are  familiar. 

Boracic  or  boric  acid.  Boracic  acid,  H3BO3,  is  a  feeble 
acid.  Its  solution  is  used  as  an  eye  wash,  and  as  a  food 
preservative. 

Tannic  acid.  The  astringent  principle  found  in  oak  and 
hemlock  bark  and  in  many  plants  is  called  tannin.  It  is  a 
mixture  of  a  number  of  compounds,  and  is  used  in  dyeing, 
making  writing  ink,  and  tanning  leather. 

Nutgalls  contain  much  tannin.  If  you  boil  a  small 
quantity  of  powdered  nutgalls  in  water,  and  add  a  little 
ferrous  sulphate,  a  violet-colored  precipitate,  slowly  changing 


374  CHEMISTRY   IN  THE   HOME 

to  black,  forms.  When  thickened  by  the  addition  of  a  little 
gum,  this  forms  one  of  the  common  inks.  The  ink  would  be 
too  pale  when  first  used,  so  a  color  is  usually  added  to  it. 
As  the  iron  tannate  gradually  forms,  the  ink  turns  black 
on  the  paper. 

Leather  is  made  by  first  cleaning  and  dehairing  the  hide, 
and  then  soaking  it  in  a  tannin  solution.  The  gelatinous 
compounds  of  the  hide  are  gradually  made  insoluble  by  com- 
bining with  the  tannin,  and  leather  results.  There  are 
other  methods  of  making  the  hide  insoluble,  as  by  the  use  of 
chromium  compounds. 

SUMMARY 

Aluminium  oxide  is  the  mineral  corundum.  Ruby  and  sapphire 
are  impure  forms  used  as  gems.  Emery  is  an  impure  form 
used  as  an  abrasive.  Alundum  is  fused  aluminium  oxide  and 
is  used  as  an  abrasive. 

An  abrasive  is  a  material  used  to  grind  and  polish  hard  sub- 
stances. 

Carborundum  is  silicon  carbide  and  is  one  of  the  best  abrasives. 

Thermit  is  a  mixture  of  aluminium  and  iron  oxide.  It  gives  on 
ignition  an  intense  heat. 

An  alum  is  a  double  sulphate  of  aluminium  and  some  other  metal. 

Nitric  acid  is  made  by  heating  sulphuric  acid  and  a  nitrate  together. 
Nitrates  are  good  oxidizing  agents. 

Nitroglycerin  is  glyceryl  nitrate.     It  is  a  high  explosive. 

Dynamite  is  nitroglycerin  absorbed  in  some  material,  as  ground 
wood. 

Guncotton  is  cotton  hexanitrate. 

Phosphorus  is  made  by  heating  calcium  phosphate  and  carbon 
in  an  electric  furnace.  Red  and  yellow  are  two  allotropic 
forms. 

Matches  are  phosphorus  or  phosphorus  sesquisulphide,  an  oxidizing 
material,  glue,  and  an  abrasive.  Safety  matches  have  the 
composition  divided  into  two  parts,  and  one  part  is  placed  on 
the  match  box. 


SOME  COMMON  CHEMICALS  375 

Sulphur  is  obtained  from  Louisiana  by  melting  the  deposit  in  the 

ground  and  forcing  it  to  the  surface  with  compressed  air.     It 

is  a  yellow  solid,  insoluble  in  water  but  soluble  in  carbon  disul- 

phide.     Used  in  making  sulphuric  acid,  vulcanizing  rubber, 

and  in  dyestuffs. 
Sulphur  dioxide  is  prepared  by  burning  sulphur.     It  is  used  in 

bleaching  and  disinfecting. 
Sulphuric  acid  is  made  by  oxidizing  sulphur  dioxide  and  dissolving 

sulphur  trioxide  produced  in  water.     It  is  the  most  important 

acid. 
Carbon  disulphide  is  prepared  by  the  direct  union  of  carbon  and 

sulphur.     It  is  used  as  a  solvent  and  insecticide. 
Zinc  white  is  zinc  oxide  and  is  used  as  a  pigment. 
Lead  white  is  basic  lead  carbonate  and  is  used  as  a  pigment. 
Hydrogen  sulphide  is  used  in  the  laboratory  as  a  reagent. 
Oxidized  silver  is  silver  coated  with  silver  sulphide.     Other  metals 

are  colored  in  a  similar  way. 
Milk  is  a  universal  food,  easily  spoiled  and  must  be  preserved  with 

great  care. 
Pasteurizing   kills  the  lactic   acid   bacteria,   and   preserves   milk. 

It  does  not  sterilize  the  milk. 
Condensed  milk  is  milk  from  which  some  of  the  water  has  been 

evaporated. 
Milk  powder  is  milk,  usually  skimmed,  from  which  all  of  the  water 

has  been  taken. 
Homogenized  milk  is  milk  that  has  been  forced  through  minute 

orifices  to  make  it  a  more  perfect  emulsion. 
Cheese  is  the  dried  and  ripened  curd  of  milk,  produced  by  adding 

rennet  to  milk. 

Butter  is  the  collected  butter  fat  of  milk. 

Modified  milk  is  milk  so  treated  as  to  make  its  composition  re- 
semble that  of  mothers'  milk. 

Oxalic  acid  is  a  poison.     It  is  used  in  metal  polishes. 
Tartaric  acid  is  made  from  argols.     Tartrates  are  used  in  baking 

powders  and  dyeing. 
Boracic  acid  is  a  food  preservative. 
Tannin  is  used  in  making  leather  and  ink. 
Leather  is  hide  made  insoluble  by  tannin. 


376  CHEMISTRY   IN   THE   HOME 

Exercises 

1.  Why  is  sulphur  not  mined  instead  of  being  obtained  by  the 
present  method? 

2.  How  could  you  prepare  flowers  of  sulphur  in  the  laboratory? 

3.  How  could  you  blacken  a  copper  ash  tray? 

4.  Which  is  the  more  harmful  acid  if  spilled  upon  a  coat, 
dilute  sulphuric  or  hydrochloric  acid?     Why? 

5.  What  compound  gives  rotten  eggs  their  disagreeable  odor? 
Account  for  the  formation  of  this  compound. 

6.  How  would  you  fumigate  a  coat,  using  sulphur  dioxide? 

7.  Sulphur  dioxide  is  sometimes  used  in  drying  fruits.     Do  you 
consider  this  objectionable? 

8.  How  could  you  obtain  sulphur  dioxide  from  sulphuric  acid 
in  the  laboratory  ? 

9.  Have  you  any  reason  for  thinking  that  a  strong  tincture 
of  iodine  might  be  injurious?     Explain. 

10.  As  sulphuric  acid  takes  no  part  in  the  chemical  change,  why 
is  it  used  in  the  preparation  of  nitroglycerin  ? 

11.  Carbon  disulphide  is  used  to  kill  mice  in  grain.     Is  there 
any  danger  in  using  it  ?     What  precautions  would  you  take  ? 

12.  Why  does  ammonia  not  restore  the  color  of  a  dress  stained 
with  nitric  acid? 

13.  Would  you  obtain  hydrogen  by  the  action  of  strong  nitric 
acid  upon  copper?     Explain. 

14.  Why  is  the  paper  label  on  the  outside  of  the  sulphuric  acid 
bottle  often  blackened  ? 

15.  Give  two  reasons  for  the  severe  burns  caused  by  sulphuric 
acid. 

16.  Caesium,  atomic  weight  132.8,  is  a  member  of  the  sodium 
family.     Tell  its  properties. 

17.  Rubidium,  atomic  weight  85.5,  is  a  member  of  the  sodium 
family.     Will  it  decompose  water  more  or  less  energetically  than 
potassium?    How  do  you  know? 

18.  Why  is  milk  often  the  transmitting  agent  for  typhoid  fever? 

19.  If  formaldehyde  will  preserve  milk,  why  not  use  it? 

20.  Is  there  any  difference  between  pasteurized  and  sterilized 
milk?     Explain. 

21.  How  would  you  obtain  milk  sugar,  starting  with  raw  milk? 


APPENDIX 


METRIC    MEASUREMENTS 

The  nomenclature  in  the  metric  system  is  extremely  simple, 
since  there  is  one  general  principle  which  applies  to  all  tables  of 
measurements.  The  Greek  prefixes  for  10,  100,  1000,  viz.,  deca, 
hccto,  and  kilo,  are  used  to  signify  multiplication ;  while  the 
Latin  prefixes  for  10,  100,  and  1000,  viz.,  deci,  centi,  and  milli, 
are  employed  to  express  division. 

The  principle  is  illustrated  in  the  following  table  of  linear 

measure : 

LINEAR  MEASURE 


Divisions  . 
Unit      .     . 
Multiples  . 

("MILLIMETER 
.  ^  CENTIMETER 
{  Decimeter 
.      METER 
r  Decameter 
.  1  Hectometer 
(  KILOMETER 

— 

0.001  me 
0.01 
0.1 
1 
10 
100 
1000 

ber, 

of  a  meter 


The  only  units  of  cubic  capacity  that  we  need  to  use  are  the 
cubic  centimeter  (cc.)  and  the  liter  (1.)  which  is  1000  cc.  and  is 
roughly  equivalent  to  1  quart. 

The  weight  of  1  cc.  of  distilled  water  at  4°  C.  is  called  1  gram. 

A  kilogram  is  1000  grams.     1  liter  of  water  weighs  1  kilogram. 


METRIC  AND  ENGLISH  EQUIVALENTS 


1m. 
1  m. 

m. 

Km. 

sq.  cm 

sq 

sq.  m. 

cc. 

cu.  m. 

cu.  m. 

1. 

1. 


fe*. 


=  39.37  in. 
=  3.2809  ft. 
=  1.0936  yd. 
=  0.62137  mi. 
=  0.1550sq.  in. 
m.    =  10.7Q4  sq.  ft. 
=  1.196  sq.  yd. 
=  0.06102  cu.  in. 
=  35.314  cu.  ft. 
=  1.3080  cu.  yd. 
=  0.26417  gal. 
=  0.9081  dry  qt. 
=  15.4324  gr. 
=  2.2046  Ib.  avoir. 
=  0.03527  oz. 


1  in. 
1ft. 
lyd. 
1  mi. 
1  sq.  in. 
1  sq.  ft. 
1  sq.  yd. 
1  cu.  in. 
1  cu.  ft. 
1  fluid  oz. 
1  liquid  qt. 
1  dry  qt. 


=  2.5400  cm. 
=  30.480  cm. 
=  0.91440  m. 
=  1.60935  Km. 
=  6.452  sq.  cm. 
=  929.0  sq.  cm. 
=  0.8361  sq.  m. 
=  16.387  cc. 
=  28316  cc. 
=  29.574  cc. 
=  0.94636  1. 
=  1.101  1. 


1  gr.  =  0.0648  g. 

1  Ib.  avoir.  =  453.59  g. 
1  oz.  avoir.  =  28.3495  g. 


377 


378 


APPENDIX 


PHYSICAL  CONSTANTS  OF  COMMON  ELEMENTS 


ELEMENT 

SYMBOL 

ATOMIC 

WEIGHTS 

VALENCE 

SPECIFIC  GRAVITY 

MELTING 
POINT 

BOILING 
POINT 

Ap- 
proxi- 
mate 

Exact 
O=  16 

Water  =  1 

Air=l 

°C. 

°C. 

Aluminium 

Al 

27 

27.1 

III 

2.6 

660 

1600 

Antimony 

Sb 

120 

120.2 

III  V 

6.6 

630 

1600 

Argon 

A 

40 

39.88 

1.38 

-188 

-186 

Arsenic 

As 

75 

74.96 

III  V 

5.7 

185 

449.5 

Barium 

Ba 

137 

137.37 

II 

3.8 

850 

950 

Bismuth 

Bi 

-208 

208.0 

III  V 

9.7 

269 

1435 

Boron 

B 

11 

11.0 

III 

2.6 

infu- 

3500 

sible 

Bromine 

Br 

80 

79.92 

I 

3.1 

-7.3 

63 

Cadmium 

Cd 

112 

112.4 

II 

8.6 

322 

778 

Calcium 

Ca 

40 

40.07 

II 

1.5 

800 



Carbon 

C 

12 

12.00 

IV 

1.7-2.1 

sub- 

3500 

limes 

Chlorine 

Cl 

35.5 

35.45 

I 

2.49 

-102 

-33.6 

Chromium 

Cr 

52 

52.0 

II  III 

6.9 

1515 



VI 

Copper 

Cu 

63.6 

63.57 

I  II 

8.7 

1090 

2100 

Fluorine 

F 

19 

19.0 

I 

1.31 

-223 

-187 

Gold 

Au 

197 

197.2 

I  III 

19.3 

1064 



Helium 

He 

4 

4.0 



0.13 

-271 

-267 

Hydrogen 

H 

1 

1.008 

I 

0.07 

-256.5 

-252.5 

Iodine 

I 

127 

126.92 

I 

4.9 

114 

184 

Iron 

Fe 

56 

55.84 

II  III 

7.8 

1804 



Lead 

Pb 

207 

207.1 

II  IV 

11.3 

327 

1500 

Magnesium 

Mg 

24.3 

24.32 

II 

1.7 

632 

1100 

Manganese 

Mn 

55 

55.0 

II  IV 

7.4 

1245 



Mercury 

Hg 

200 

200.6 

I  II 

'    13.6 

39.5 

357 

Nickel 

Ni 

58.7 

58.68 

II 

8.7 

1484 



Nitrogen 

N 

14 

14.01 

III  V 

0.96 

-210 

-196 

Oxygen 

O 

16 

16.00 

II 

1.10 

-230 

-182 

Phosphorus 

P 

31 

31.04 

III  V 

1.8 

44.2 

290 

Platinum 

Pt 

195 

195.2 

IV 

21.5 

1750 



Potassium 

K 

39 

39.10 

I 

0.87 

62.5 

757 

Silicon 

Si 

28 

28.3 

IV 

2.0 

1400 

3500 

Silver 

Ag 

108 

107.88 

I 

10.5 

961 

2050 

Sodium 

Na 

23 

23. 

I 

0.97 

97.6 

877 

Sulphur 

S 

32 

32.07 

II  IV  VI 

2.0 

114.5 

445 

Tin 

Sn 

119 

119.0 

II  IV 

7.3 

232 

1500 

Zinc 

Zn 

65.4 

65.37 

II 

7.1 

419 

918 

INDEX 


Abrasive,  355. 

Absolute  zero  defined,  79. 

Acetanilide,  209. 

Acetylene  series,  204. 

Acids,     bases,     and    salts     (Chapter 

XII),  130. 
Acids,  fatty,  206. 

organic,  205. 

typical,  130. 

typical  properties,  131. 
Agate,  306. 
Air,  96. 

composition  of,  104. 

cycle,  107. 
Albumin,  247. 
Alchemists,  48. 
Alcohol,  denatured,  290. 

ethyl,  289. 

grain,  289. 

properties,  290. 

wood,  290. 
Alcohols,  205. 
Aldehydes,  205. 
Alkalies,  132. 
Alkaloids,  248. 
Alloys,  163. 
Alum,  357. 
Aluminium,  manufacture,  159. 

oxide,  355. 

properties,  159. 

uses,  160. 
Alundum,  355. 
Amalgams,  164. 
Amethyst,  305. 

Ammonia     and      ammonium      com- 
pounds (Chapter  XIV),  145. 
Ammonia,     commercial    production, 
146. 

preparation,  145. 

properties,  145. 
Ammonium,  147. 


Ammonium,  carbonate,  148. 

chloride,  147. 
Amorphous,  34. 
Analysis  denned,  23. 
Aniline,  209. 
Antifebrine,  209. 
Antiseptics,  300. 
Asbestos,  318. 

Atmosphere  (Chapter  IX),  96. 
Atom,  defined,  52. 

symbol  of,  54. 

Atomic  theory  (Chapter  VI),  48. 
Atomic  weight,  defined,  109. 

table -of,  378. 

Bacteria,  action  on  protein,  296. 

nitrifying,  294. 

pathogenic,  293. 

reproduction  of,  292. 

sterilization,  295. 

where  found,  295. 
Baking     powders     (Chapter     XIX), 

195. 
Baking  powders,  134,  196. 

alum,  198. 

home-made,  200. 

phosphate,  198. 

tartrate,  196. 
Barometer,  97. 

uses,  99. 

Bases,  typical  properties,  132. 
Benzol,  208. 
Bleaching,  328. 

powder,  126,  343. 

sulphur  dioxide,  328. 
Bluing,  328. 
Boiling,  effects  of  altitude  on,  85. 

effects  of  dissolved  substance  on,  85. 

effects  of  pressure  on,  85. 

explained,  83. 
Bone  black,  182. 


379 


380 


INDEX 


Boracic  acid,  373. 

Borax,  143. 

Bread,  leavening,  196. 

making,  288. 
Brick,  311. 
Bromine,  367. 
Bunsen  burner,  69. 
Butane,  202. 
Butter,  372. 
Butterine,  216. 

Caffeine,  248. 

Calcium  and   its  compounds  (Chap- 
ter XXIX),  336. 
Calcium,  336. 

carbonate,  336. 

hydroxide,  341. 

oxide,  341. 

phosphate,  343. 

sulphate,  340. 

super-phosphate,  343. 
Calorie  denned,  78. 
Calorimeter,  respiration,  257. 
Cane  sugar,  225. 

Carbohydrates  (Chapter  XXII),  225. 
Carbohydrates  denned,  225. 
Carbolic  acid,  301. 

Carbon  and   its   compounds    (Chap- 
ter XVII),  175. 
Carbon,  175. 
Carbon  dioxide,  preparation,  188. 

properties,  188. 

test  for,  190. 

uses,  189. 

utilization  by  plants,  191. 
Carbon  disulphide,  365. 
Carbon  monoxide,  191. 
Carbon  tetrachloride,  63. 
Carborundum,  356. 
Casein,  247. 
Cast  iron,  153. 
Catalytic  agent,  39,  288. 
Caves,  formation  of,  338. 
Celluloid,  241. 
Cellulose,  240. 
Cement,  314. 
Centrifugal  force,  229. 
Centrifugal  separators,  229. 
Chalk,  336. 
Charcoal,  182. 
Cheese,  372. 
Chemical  change  defined,  56. 


Chemistry      of      cooking      (Chapter 

XXVIII),  332. 
Chlorine  (Chapter  XI),  123. 
Chlorine,  preparation,  123. 

properties,  126,  367. 

uses,  127. 
Chlorophyll,  283. 
Cinchona,  249. 
Clay,  311. 
Coal,  anthracite,  176. 

bituminous,  176. 

brown,  177. 

composition  of,  178. 

lignite,  176. 
Cocaine,  248. 
Cocoa  butter,  215. 
Coke,  178. 
Colors,  see  Dyes. 
Combustion  (Chapter  VII),  58. 
Combustion  defined,  58. 

spontaneous,  60. 
Compounds,  defined,  24. 

naming,  110. 
Concrete,  314. 

reenforced,  314. 
Condiments,  food  value,  260. 
Conduction,  85. 
Conductivity  of  materials,  87. 
Convection,  88. 
Copper,  163. 
Coquina,  340. 
Coral,  339. 
Cotton,  319. 
Cream  of  tartar,  197. 
Creosote,  209. 
Crystal  defined,  33. 
Crystalline,  34. 
Crystallization,  33. 

water  of,  34. 

Deliquescence  defined,  35. 
Density  defined,  15. 
Deodorizers,  300. 
Developing,  photographic,  168. 
Dew,  101. 
Dew  point,  101. 
Dextrin,  236. 
Diamond,  184. 
Diatomaceous  earth,  306. 
Disinfectant,  300. 
Distillation,  21. 
fractional,  22,  82. 


INDEX 


381 


Dyes  and  dyeing  (Chapter  XXX,)  346. 
Dyes,  acid,  350. 

alizarin,  352. 

aniline  black,  352. 

basic,  351. 

bleeding,  351. 

care  necessary,  346. 

direct,  351. 

fast,  348. 

natural,  349. 

sulphur,  352. 
Dynamite,  358. 

Efflorescence  denned,  34. 
Electrolysis,  123. 
Element  denned,  23. 
Emery,  355. 
Emulsion  defined,  27. 
Energy,  76. 
Energy,  radiant,  91. 
Enzymes,  287. 
Equations,  chemical,  113. 
Esters,  205. 
Ether,  anaesthetic,  291. 

luminiferous,  89. 
Ethylene  series,  203. 
Evaporation,  83. 
Expansion,  81. 

Fabrics,  fireproofing,  63. 
Fats,  207. 

extraction  of,  216. 
Fermented  drinks,  289. 
Ferments,  287. 
Fibers,  animal,  318. 

characteristics  of,  316. 

glass,  318. 

vegetable,  318. 
Filters,  29. 
Filtrate  defined,  29. 
Filtration,  29. 
Fire  extinguishers,  190. 

extinguishing  of,  63. 

regulation  of,  65. 
Fireless  cooker,  92. 
Flame,  luminous,  68. 
Flatiron,  gas,  73. 
Flint,  306. 
Fluorine,  366. 
Flux  in  blast  furnaces,  151. 
Food,  advantages  of  cooking,  332. 

calories  in,  257. 


Food,  carbohydrates,  246. 

defined,  250. 

economy  in  buying,  256. 

efficiency  in  buying,  255. 

inorganic,  250. 

organic,  251. 

preservation  of,  298. 

tables,  261-271,  274-281. 
Food  preservation  (Chapter  XXIV), 

283. 

Foods  (Chapter  XXIII),  250. 
Formaldehyde,  301. 
Formulas  (Chapter  X),  109. 
Formulas,  empirical,  118. 

graphic,  119. 

rational,  118. 
Frost,  101. 
Frying,  333. 
Fuels,  65. 
Fungi,  283. 
Furnace,  blast,  152. 

reverberatory,  154. 

Gas,  illumination,  178. 

meter,  71. 

natural,  181. 

water,  192. 
Gases  defined,  80. 
Gasoline,  180. 
Gelatin,  248. 
Germicide,  300. 
Glass,  bottles,  309. 

chemical,  310. 

cut,  310. 

ground,  310. 

manufacture  of,  307. 

plate,  309. 

tubes,  310. 

water,  143. 

Glassware,  graduating,  311. 
Glucose,  234. 

manufacture  of,  236. 
Gluten,  248. 
Glycerin,  219. 
Gold,  161. 
Grape  sugar,  237. 
Graphite,  183. 
Guncotton,  358. 
Gypsum,  340. 

Halogens,  366. 
Hard  water,  343. 


382 


INDEX 


Heat  (Chapter  VIII),  76. 
Heat,  effects  of,  81. 

sources  of,  80. 

transferring  of,  85. 
Hot  water  bottle,  36. 
Humidity,  absolute,  101. 

effects  of,  102. 

relative,  101. 

Hydrocarbons     and     derived     com- 
pounds (Chapter  XX),  202. 
Hydrocarbons,  202. 
Hydrochloric  acid,  preparation,  130. 

properties  of,  131. 
Hydrogen  (Chapter  V),  44. 
Hydrogen,  occurrence,  44. 

preparation,  44. 

properties  of,  45. 

uses  of,  46. 
Hydrogen  peroxide,  42. 

uses  of,  43. 

Hydrogen  sulphide,  364. 
Hydrolysis,  208. 
Hydroxyl,  112. 
Hygroscopic  defined,  35. 

Ice,  artificial,  93. 
Iceland  spar,  337. 
Illuminating  gas,  178,  192. 
Image,  latent,  169. 
Indelible  ink,  167. 
Indicator,  132. 
Indigo,  synthetic,  120,  350. 
Infusorial  earth,  306. 
Ink,  373. 

eradicators,  129. 

indelible,  167. 
Iodine,  367. 
Iron,  cast,  153. 

galvanized,  158. 

metallurgy  of,  150. 

rusting  of,  157. 

wrought,  153. 

Javelle  water,  128,  328. 

Kerosene,  67. 

lamp,  67. 

Kindling  temperature  denned,  59. 
Kumiss,  289,  373. 

Lactose,  234. 
Lakes,  349. 
Lampblack,  182. 


Laundry  chemistry  (Chapter  XXVII), 

325. 
Law,  conservation  of  energy,  77. 

conservation  of  matter,   13. 

definite  proportions,  24,  49. 

indestructibility  of  matter,  13. 

of  multiple  proportions,  49. 

periodic,  367. 

radiant  energy,  91. 
Lead,  161. 

white,  366. 
Leather,  374. 

Light,  chemical  action  of,  166. 
Lime,  quick,  341. 

slaked,  341. 
Limestone,  336. 
Limewater,  342. 
Linen,  320. 
Linoleum,  218. 
Liquids  defined,  80. 
Litmus,  132. 
Luminosity  of  flame,  68. 
Lunar  caustic,  167. 

Maltose,  234. 

Marble,  337. 

Market  list,  273. 

Matches,  359. 

Matter,  composition  of,  51. 

Meat,  cooking  of,  334. 

frying,  333. 

simmering,  333. 
Metals  (Chapter  XV),  149 
Metals,  149. 

obtaining  of,  150. 
Methyl  alcohol,  290. 
Metric  system,  377. 
Milk,  composition  of,  370. 

condensed,  371. 

homogenized,  372. 

pasteurized,  296,  371. 

powdered,  371. 

sugar,  234. 
Mixtures  defined,  24. 
Molds,  284. 

flavors  due  to,  286. 

how  to  avoid,  285. 

spores,  285. 

Molecular  weight  defined,  109. 
Molecule  defined,  51. 
Mordants,  349. 
Mortar,  342. 


INDEX 


383 


Naphthalene,  209. 
Nascent  state,  209. 
Negative,  photographic,  170. 

fixing,  171. 

Neutralization,  130,  134. 
Nickel  plate,  158. 
Nicotine,  248. 
Nitric  acid,  357. 
Nitrobenzol,  209. 
Nitrogen,  103. 
Nitroglycerin,  358. 
Nonmetals,  149. 

Oil,  cottonseed,  214. 

crude,  180. 

extracting,  211. 

fixed,  213. 

linseed,  214. 

nondrying,  213. 

olive,  215. 

palm,  215. 

peanut,  215. 

semidrying,  213. 

sesame,  215. 
Oilcloth,  217. 
Oils,  fats,  and  soaps  (Chapter  XXI), 

211. 

Oils,  207. 

Oleomargarine,  216. 
Opal,  305. 

Organic  chemistry,  175. 
Oxalic  acid,  373. 
Oxidation,  40. 

slow,  58. 
Oxides,  40. 
Oxides  of  carbon  (Chapter  XVIII), 

188. 

Oxidizing  agents,  40. 
Oxygen      and      hydrogen      peroxide 

(Chapter  IV),  38. 
Oxygen,  occurrence  of,  38. 

preparation  of,  38. 

properties  of,  40. 
Oxy hydrogen  blowpipe,  45. 
Ozone,  41. 

uses  of,  41. 

Palm  oil,  215. 
Panchromatic  plates,  171. 
Paper,  hand  made,  241. 

machine  made,  242. 

wood  pulp,  244. 


Paraffin  series,  202. 
Pasteurization  of  milk,  296. 
Pearls,  337. 
Pepsin,  288. 
Petroleum,  180. 
Phenol,  209. 
Phlogiston,  77. 
Phosphorus,  358. 
Photographic  films,  169. 

plates,  169. 

Photography  (Chapter  VI),  166. 
Physical      and      chemical      changes 

(Chapter  I),  9. 
Physical  changes,  10. 

defined,  56. 
Plaster,  342. 
Plaster  of  Paris,  340. 
Porcelain,  312. 
Positive,  photographic,  170. 
Potassium,  144. 
Preservation      of      Food      (Chapter 

XXIV),  283. 

Preservation  of  food,  by  canning,  297. 
Preservatives,  chemical,  298. 
Pressure  cooker,  17. 
Pressure,  effect  on  boiling  point,  17. 
Prints,  blue,  172. 
Problems,  chemical,  120. 
Propane,  202. 
Protein,  247. 

excessive  in  food,  259. 

how  to  cook,  332. 
Ptomaines,  247. 
Ptyalin,  288. 
Puddling,  154. 
Putty,  337. 

Quartz,  304. 
Quicklime,  341. 
Quinine,  249. 

Radiation,  89. 
Radicals,  112. 
Rain,  causes  explained,  18. 
Rations,  balanced,  258. 

boys  and  girls,  259. 
Refrigerator,  86. 
Relative  humidity,  101. 
Replacement  of  elements,  135. 
Residue  defined,  29. 
Reverberatory  furnace,  154. 
Rochelle  salt,  198. 


384 


INDEX 


Saccharin,  246. 
Saleratus,  142. 
Salt,  table,  138,  141. 

uses  of,  141. 
Salts,  formation  of,  133. 
Sand,  306. 
Sandpaper,  306. 
Saponification,  219. 
Shoddy,  321. 
Silica,  306. 
Silicates,  307. 
Silicon,  304. 
Silicon  dioxide,  304. 
Silicon,  silica,  and  silicates  (Chapter 

XXV),  304. 
Silk,  321. 

artificial,  323. 

weighting,  349. 
Silver,  162. 

nitrate,  166. 
Simmering,  333. 
Slag,  blast  furnace,  152. 
Slaked  lime,  341. 
Smelling  salts,  148. 
Soap,  219. 

action  on  hard  water,  223. 

cold  process,  223. 

fats,  222. 

powders,  222. 

scouring,  222. 

transparent,  223. 

uses  of,  329. 
Soda,  baking,  142. 

biscuits,  135. 

washing,  141. 
Sodium  and  its  compounds  (Chapter 

XIII),  137. 
Sodium,  action  on  water,  138. 

bicarbonate,  142. 

carbonate,  141. 

chloride,  138. 

hydroxide,  132. 

nitrate,  143. 

properties  of,  137. 

salts,  143. 

silicates,  143. 

stearate,  219. 
Solids  denned,  80. 
Solio,  173. 
Solute,  31. 

Solution  (Chapter  III),  27. 
Solution,  concentrated,  30. 


Solution,  defined,  28. 

explained,  27. 

of  gases,  31. 

of  liquids,  31. 

saturated,  30. 

supersaturated,  35. 
Solvent,  31. 
Some    common    chemicals    (Chapter 

XXXI) ,  354. 

Specific  gravity  defined,  88. 
Sprinkler  system,  163. 
Stains,  acid,  327. 

removal  of,  by  absorption,  327. 

removal  of,  by  solution,  325, 
Stalactites,  339. 
Stalagmites,  339. 
Starch,  237. 

commercial  form  of,  239. 
Steam,  16. 
Steel,  Bessemer,  155. 

crucible,  155. 

hardening  of,  156. 

open  hearth,  155. 
Sterilization,  295. 
Stoneware,  311. 
Stove  gas,  74. 
Sublimation,  82. 
Sugar,  beet,  230. 

boiling  of,  232. 

cane,  225. 

invert,  228. 

maple,  231. 

refining,  227. 

sorghum,  232. 
Sulphur,  360. 

dioxide,  301,  361. 

trioxide,  361. 
Sulphuric  acid,  362. 
Suspension  defined,  28. 

explained,  28. 

Tannic  acid,  373. 

Tartaric  acid,  373. 

Textiles  (Chapter  XXVI),  316. 

Theine,  248. 

Theobromine,  248. 

Theory,  atomic,  51. 

Thermit,  356. 

Thermometers,  Centigrade,  79. 

Fahrenheit,  79. 
Tile,  311. 
Tin,  158. 


INDEX 


385 


Tincture,  30. 
Topaz,  305'. 
Trypsin,  288. 

Valence,  115. 
Vaporization,  82. 
Vegetables,  cooking,  334. 
Ventilation,  106. 
Vinegar,  291. 
Volatilization,  82. 

Washing  powders,  329. 

Washing  soda,  141. 

Water  (Chapter  II),  14. 

Water,  composition  by  volume,  22. 

composition  by  weight,  25. 

crystallization,  34. 

cycle,  19. 

disadvantages  of  hard,  344. 

distilling,  21. 

electrolysis  of,  22. 

evaporation  of,  18. 

expansion  of,  15. 

gas,  192. 


Water,  glass,  143. 

ground,  19. 

hard,  343. 

maximum  density  of,  15. 

measuring  hardness  of,  344. 

occurrence  of,  14. 

permanent  hard,  344. 

properties  of,  14. 

purifying,  22. 

sources  of  impurities,  20. 

synthesis  of,  25. 

table,  19. 

temporary  hard,  344. 
Welsbach  burner,  70. 
Whiting,  337. 
Wool,  320. 
Work  defined,  76. 

Yeast,  287,  288. 

alcohol  production,  289. 
raising  bread,  288. 

Zero,  absolute,  79. 
Zinc  white,  366. 
Zymase,  287. 


----«  ASSESSED  f         OP25  CENTS 


LD  21-ioom-8,'34 


VB  1547 


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